diff --git a/NEWS.md b/NEWS.md
index 2739258..b51c6fb 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,11 +1,12 @@
 # Release notes
 
-## Unversioned updates
+## Version 0.5.18 (2025-11-24)
 
 ### Enhancements
 
 * Added the option `pre_plot_sub_components` to the `GUI`-constructor to skip preplotting hidden sub components of an area (the option is by default `true`). The components of an `Area` are then plotted on demand (on the `open` functionality). This greatly enhances performance for large cases.
 * Improved general performance.
+* Added two new options to the `GUI` constructor: `simplified_connection_plotting` (default `false`) for controlling connection visualization detail, and `simplify_all_levels` (default `false`) for applying simplification across hierarchical levels.
 
 ### Adjustments
 
@@ -13,6 +14,8 @@
 * Added the field `visible` to `EnergySystemDesign` and `Connection` on which plots can directly rely on for visibility
 * Adjust behaviour of `Base.show` on the types `EnergySystemDesign`, `Connection` and `AbstractSystem` to correspond to `Base.show` of their corresponding `AbstractElement`.
 * Change tests of toggling of colors to be based on a new case having more transmission modes (the case in the new `test/EMI_geography_2.jl` file).
+* Make the distance between two way connection linearly dependent on `Δh` instead of a fixed width based on `gui.vars[:two_way_sep_px]`.
+* Make the markersize (arrow heads for connections) linearly dependent on `Δh` instead of a fixed size based on `gui.vars[:markersize]`
 
 ## Version 0.5.17 (2025-11-19)
 
diff --git a/docs/generate_images.jl b/docs/generate_images.jl
index 59dc4fa..693041c 100644
--- a/docs/generate_images.jl
+++ b/docs/generate_images.jl
@@ -9,6 +9,8 @@ import EnergyModelsGUI:
     get_component,
     get_selected_systems,
     get_name,
+    get_toggle,
+    pick_component!,
     update!,
     toggle_selection_color!,
     select_data!
@@ -77,7 +79,7 @@ function create_EMI_geography_images()
     solution_summary(m)
 
     # Set folder where visualization info is saved and retrieved
-    design_path = joinpath(@__DIR__, "design", "EMI", "geography")
+    design_path = joinpath(docsdir, "design", "EMI", "geography")
 
     # Run the GUI
     gui = GUI(
@@ -90,7 +92,7 @@ function create_EMI_geography_images()
     )
 
     # Create examples.png image
-    path_to_results = joinpath(@__DIR__, "src", "figures")
+    path_to_results = joinpath(docsdir, "src", "figures")
     get_vars(gui)[:path_to_results] = path_to_results
     get_menu(gui, :axes).selection[] = "All"
     get_menu(gui, :export_type).selection[] = "png"
@@ -105,9 +107,8 @@ function create_EMI_geography_images()
 
     # Create EMI_geography.png image
     oslo_area = get_component(get_root_design(gui), 1)
-    push!(get_selected_systems(gui), oslo_area) # Manually add to :selected_systems
+    pick_component!(gui, oslo_area, :topo)
     update!(gui)
-    toggle_selection_color!(gui, oslo_area, true)
     select_data!(gui, "area_exchange")
     notify(export_button.clicks)
     mv(
@@ -119,11 +120,8 @@ function create_EMI_geography_images()
     # Create EMI_geography_Oslo.png image
     notify(open_button.clicks)
     sub_component = get_component(oslo_area, 5) # fetch node id 5 in Oslo area
-    selected_systems = get_selected_systems(gui)
-    empty!(selected_systems)
-    push!(selected_systems, sub_component) # Manually add to :selected_systems
+    pick_component!(gui, sub_component, :topo)
     update!(gui)
-    toggle_selection_color!(gui, sub_component, true)
     select_data!(gui, "cap_add")
     notify(export_button.clicks)
     mv(
diff --git a/docs/make.jl b/docs/make.jl
index 45deb3f..a8bb672 100644
--- a/docs/make.jl
+++ b/docs/make.jl
@@ -7,14 +7,16 @@ const EMB = EnergyModelsBase
 const EMGUI = EnergyModelsGUI
 
 # Copy the NEWS.md file
-news = "docs/src/manual/NEWS.md"
+pkg_dir = pkgdir(EnergyModelsGUI)
+docsdir = joinpath(pkg_dir, "docs")
+news = joinpath(docsdir, "src", "manual", "NEWS.md")
 if isfile(news)
     rm(news)
 end
-cp("NEWS.md", news)
+cp(joinpath(pkg_dir, "NEWS.md"), news)
 
 ENV["EMX_TEST"] = true # Set flag for example scripts to check if they are run as part CI
-include("generate_images.jl")
+include(joinpath(docsdir, "generate_images.jl"))
 
 DocMeta.setdocmeta!(
     EnergyModelsGUI, :DocTestSetup, :(using EnergyModelsGUI); recursive = true,
diff --git a/docs/src/figures/EMI_geography.png b/docs/src/figures/EMI_geography.png
index 2837ba5..7b43885 100644
Binary files a/docs/src/figures/EMI_geography.png and b/docs/src/figures/EMI_geography.png differ
diff --git a/docs/src/figures/EMI_geography_Oslo.png b/docs/src/figures/EMI_geography_Oslo.png
index a652c2c..2d7f0a8 100644
Binary files a/docs/src/figures/EMI_geography_Oslo.png and b/docs/src/figures/EMI_geography_Oslo.png differ
diff --git a/ext/EMGExt/EMGExt.jl b/ext/EMGExt/EMGExt.jl
index ea8485e..12115e1 100644
--- a/ext/EMGExt/EMGExt.jl
+++ b/ext/EMGExt/EMGExt.jl
@@ -166,7 +166,7 @@ Get the line style for an Transmission `transmission` based on its properties.
 """
 function EMGUI.get_linestyle(gui::GUI, transmission::Transmission)
     return [
-        EMI.has_investment(m) ? EMGUI.get_var(gui, :investment_lineStyle) : :solid for
+        EMI.has_investment(m) ? EMGUI.get_var(gui, :investment_linestyle) : :solid for
         m ∈ modes(transmission)
     ]
 end
diff --git a/src/datastructures.jl b/src/datastructures.jl
index 5a53811..7302a9b 100644
--- a/src/datastructures.jl
+++ b/src/datastructures.jl
@@ -1,7 +1,7 @@
 """
     AbstractGUIObj
 
-Supertype for EnergyModelsGUI objects representing `Node`s/`Link`s/`Area`s/`Transmission`s.
+Supertype for `EnergyModelsGUI` objects representing `Node`s/`Link`s/`Area`s/`Transmission`s.
 """
 abstract type AbstractGUIObj end
 
@@ -15,14 +15,14 @@ struct NothingDesign <: AbstractGUIObj end
 """
     AbstractSystem
 
-Supertype for EnergyModelsGUI objects representing a sub system of a Case.
+Supertype for `EnergyModelsGUI` objects representing a sub system of a `Case`.
 """
 abstract type AbstractSystem <: AbstractCase end
 
 """
     NothingElement <: AbstractElement
 
-Type for representing an empty Element (the "nothing" element).
+Type for representing an empty `AbstractElement` (the "nothing" element).
 """
 struct NothingElement <: AbstractElement end
 
@@ -139,6 +139,8 @@ energy system designs in Julia.
 - **`inv_data::ProcInvData`** stores processed investment data.
 - **`plots::Vector{Makie.AbstractPlot}`** is a vector with all Makie object associated with 
   this object.
+- **`simplified::Observable{Bool}`** indicates whether the system uses a simplified 
+  representation of its plotted connections, observed for changes.
 """
 mutable struct EnergySystemDesign <: AbstractGUIObj
     system::AbstractSystem
@@ -155,6 +157,7 @@ mutable struct EnergySystemDesign <: AbstractGUIObj
     visible::Observable{Bool}
     inv_data::ProcInvData
     plots::Vector{Makie.AbstractPlot}
+    simplified::Observable{Bool}
 end
 function EnergySystemDesign(
     system::AbstractSystem,
@@ -184,7 +187,8 @@ function EnergySystemDesign(
         file,
         visible,
         ProcInvData(),
-        Any[],
+        Makie.AbstractPlot[],
+        Observable(false),
     )
 end
 
@@ -201,30 +205,42 @@ Mutable type for providing a flexible data structure for connections between
 - **`to::EnergySystemDesign`** is the `EnergySystemDesign` to which the connection is
   linked to.
 - **`connection::AbstractElement`** is the EMX connection structure.
+- **`parent::EnergySystemDesign`** is the parent EnergySystemDesign of the connection.
 - **`colors::Vector{RGBA{Float32}}`** is the associated colors of the connection.
-- **`visible::Observable{Bool}`** indicates whether the system is visible, observed for changes.
 - **`inv_data::ProcInvData`** stores processed investment data.
-- **`plots::Vector{Makie.AbstractPlot}`** is a vector with all Makie object associated with 
-  this object.
+- **`regular_plots::Vector{Makie.AbstractPlot}`** is a vector with 
+  all regular plots associated with the connection.
+- **`simplified_plots::Vector{Makie.AbstractPlot}`** is a vector with 
+  all simplified plots associated with the connection.
 """
 mutable struct Connection <: AbstractGUIObj
     from::EnergySystemDesign
     to::EnergySystemDesign
     connection::AbstractElement
+    parent::EnergySystemDesign
     colors::Vector{RGBA{Float32}}
-    visible::Observable{Bool}
     inv_data::ProcInvData
-    plots::Vector{Makie.AbstractPlot}
+    regular_plots::Vector{Makie.AbstractPlot}
+    simplified_plots::Vector{Makie.AbstractPlot}
 end
 function Connection(
     from::EnergySystemDesign,
     to::EnergySystemDesign,
     connection::AbstractElement,
+    parent::EnergySystemDesign,
     id_to_color_map::Dict{Any,Any},
-    visible::Observable{Bool},
 )
     colors::Vector{RGBA{Float32}} = get_resource_colors(connection, id_to_color_map)
-    return Connection(from, to, connection, colors, visible, ProcInvData(), Any[])
+    return Connection(
+        from,
+        to,
+        connection,
+        parent,
+        colors,
+        ProcInvData(),
+        Makie.AbstractPlot[],
+        Makie.AbstractPlot[],
+    )
 end
 
 """
@@ -446,13 +462,6 @@ Returns the `system` field of a `EnergySystemDesign` `design`.
 """
 get_system(design::EnergySystemDesign) = design.system
 
-"""
-    get_parent(design::EnergySystemDesign)
-
-Returns the `parent` field of a `EnergySystemDesign` `design`.
-"""
-get_parent(design::EnergySystemDesign) = design.parent
-
 """
     get_element(design::EnergySystemDesign)
 
@@ -535,10 +544,24 @@ EMB.get_time_struct(design::EnergySystemDesign) = EMB.get_time_struct(get_system
 """
     get_ref_element(design::EnergySystemDesign)
 
-Returns the `ref_element` field of a `EnergySystemDesign` `design`.
+Returns the `ref_element` field in the `system` field of a `EnergySystemDesign` `design`.
 """
 get_ref_element(design::EnergySystemDesign) = get_ref_element(get_system(design))
 
+"""
+    get_plots(design::EnergySystemDesign)
+
+Returns the `plots` field of a `EnergySystemDesign` `design`.
+"""
+get_plots(design::EnergySystemDesign) = design.plots
+
+"""
+    get_simplified(design::EnergySystemDesign)
+
+Returns the `simplified` field of a `EnergySystemDesign` `design`.
+"""
+get_simplified(design::EnergySystemDesign) = design.simplified
+
 """
     get_from(conn::Connection)
 
@@ -567,6 +590,43 @@ Returns the `colors` field of a `Connection` `conn`.
 """
 get_colors(conn::Connection) = conn.colors
 
+"""
+    get_regular_plots(conn::Connection)
+
+Returns the `regular_plots` field of a `Connection` `conn`.
+"""
+get_regular_plots(conn::Connection) = conn.regular_plots
+
+"""
+    get_simplified_plots(conn::Connection)
+
+Returns the `simplified_plots` field of a `Connection` `conn`.
+"""
+get_simplified_plots(conn::Connection) = conn.simplified_plots
+
+"""
+    get_simplified(conn::Connection)
+
+Returns the `simplified` field of the parent `EnergySystemDesign` of a `Connection` `conn`.
+"""
+get_simplified(conn::Connection) = get_simplified(get_parent(conn))
+
+"""
+    get_plots(conn::Connection)
+
+Returns the active `plots` field of a `Connection` `conn`.
+"""
+get_plots(conn::Connection) =
+    get_simplified(conn)[] ? get_simplified_plots(conn) : get_regular_plots(conn)
+
+"""
+    get_plots(conn::Connection, simplified::Bool)
+
+Returns the `plots` field of a `Connection` `conn` based on the `simplified` flag.
+"""
+get_plots(conn::Connection, simplified::Bool) =
+    simplified ? get_simplified_plots(conn) : get_regular_plots(conn)
+
 """
     get_inv_times(data::ProcInvData)
     get_inv_times(design::AbstractGUIObj)
@@ -602,18 +662,18 @@ Returns the `inv_data` field of a `AbstractGUIObj` `obj`.
 get_inv_data(obj::AbstractGUIObj) = obj.inv_data
 
 """
-    get_plots(obj::AbstractGUIObj)
+    get_visible(obj::AbstractGUIObj)
 
-Returns the `plots` field of a `AbstractGUIObj` `obj`.
+Returns the `visible` field of a `AbstractGUIObj` `obj`.
 """
-get_plots(obj::AbstractGUIObj) = obj.plots
+get_visible(obj::AbstractGUIObj) = obj.visible
 
 """
-    get_visible(obj::AbstractGUIObj)
+    get_parent(obj::AbstractGUIObj)
 
-Returns the `visible` field of a `AbstractGUIObj` `obj`.
+Returns the `parent` field of a `AbstractGUIObj` `obj`.
 """
-get_visible(obj::AbstractGUIObj) = obj.visible
+get_parent(obj::AbstractGUIObj) = obj.parent
 
 """
     get_fig(gui::GUI)
diff --git a/src/setup_GUI.jl b/src/setup_GUI.jl
index 26fca5c..6fd8851 100644
--- a/src/setup_GUI.jl
+++ b/src/setup_GUI.jl
@@ -46,6 +46,11 @@ to the old EnergyModelsX `case` dictionary.
   sub-components of areas in the topology design. Setting this to `false` greatly
   enhances performance for large cases, as the components of an `Area` are then
   plotted on demand (on the `open` functionality).
+- **`simplified_connection_plotting::Bool=false`** toggles whether or not to use a
+  simplified representation of the connections with a single line for each connection
+  (instead of multiple lines for multiple transmission modes) in the topology design.
+- **`simplify_all_levels::Bool=false`** toggles whether or not to use simplified connection 
+  plotting for all hierarchical levels.
 
 !!! warning "Reading model results from CSV-files"
     Reading model results from a directory (*i.e.*, `model::String` implying that the results
@@ -77,6 +82,8 @@ function GUI(
     enable_data_inspector::Bool = true,
     use_geomakie::Bool = true,
     pre_plot_sub_components::Bool = true,
+    simplified_connection_plotting::Bool = false,
+    simplify_all_levels::Bool = false,
 )
     # Generate the system topology:
     @info raw"Setting up the topology design structure"
@@ -98,7 +105,6 @@ function GUI(
         :Δh => Observable(0.05f0),  # Sidelength of main box
         :coarse_coast_lines => coarse_coast_lines,
         :Δh_px => 50,               # Pixel size of a box for nodes
-        :markersize => 15,          # Marker size for arrows in connections
         :boundary_add => 0.2f0,     # Relative to the xlim/ylim-dimensions, expand the axis
         :line_sep_px => 2,          # Separation (in px) between lines for connections
         :connection_linewidth => 2, # line width of connection lines
@@ -107,9 +113,8 @@ function GUI(
         :linewidth => 1.2,          # Width of the line around boxes
         :parent_scaling => 1.1,     # Scale for enlargement of boxes around main boxes for nodes for parent systems
         :icon_scale => 0.9f0,       # scale icons w.r.t. the surrounding box in fraction of Δh
-        :two_way_sep_px => 10,      # No pixels between set of lines for nodes having connections both ways
         :selection_color => GREEN2, # Colors for box boundaries when selection objects
-        :investment_lineStyle => Linestyle([1.0, 1.5, 2.0, 2.5] .* 5), # linestyle for investment connections and box boundaries for nodes
+        :investment_linestyle => Linestyle([1.0, 1.5, 2.0, 2.5] .* 5), # linestyle for investment connections and box boundaries for nodes
         :path_to_results => path_to_results, # Path to the location where axes[:results] can be exported
         :plotted_data => [],
         :periods_labels => periods_labels,
@@ -122,6 +127,9 @@ function GUI(
         :tol => tol,
         :use_geomakie => use_geomakie,
         :pre_plot_sub_components => pre_plot_sub_components,
+        :simplified_connection_plotting => simplified_connection_plotting,
+        :simplify_all_levels => simplify_all_levels,
+        :marker_to_box_ratio => 0.4, # Ratio between marker size and `Node` box size
         :autolimits => Dict(
             :results_op => true,
             :results_sc => true,
@@ -501,9 +509,20 @@ function create_makie_objects(vars::Dict, design::EnergySystemDesign)
         justification = :right,
     )
     expand_all_toggle = Makie.Toggle(gridlayout_taskbar[1, 8]; active = vars[:expand_all])
+    Makie.Label(
+        gridlayout_taskbar[1, 9],
+        "Simplified:";
+        halign = :right,
+        fontsize = vars[:fontsize],
+        justification = :right,
+    )
+    simplified_toggle = Makie.Toggle(
+        gridlayout_taskbar[1, 10];
+        active = vars[:simplified_connection_plotting],
+    )
 
     # Add the following to add flexibility
-    Makie.Label(gridlayout_taskbar[1, 9], " "; tellwidth = false)
+    Makie.Label(gridlayout_taskbar[1, 11], " "; tellwidth = false)
 
     # Add buttons related to the ax_results object (where the optimization results are plotted)
     Makie.Label(
@@ -664,7 +683,8 @@ function create_makie_objects(vars::Dict, design::EnergySystemDesign)
     )
 
     # Collect all toggles into a dictionary
-    toggles::Dict{Symbol,Makie.Toggle} = Dict(:expand_all => expand_all_toggle)
+    toggles::Dict{Symbol,Makie.Toggle} =
+        Dict(:expand_all => expand_all_toggle, :simplified => simplified_toggle)
 
     # Collect all axes into a dictionary
     axes::Dict{Symbol,Makie.Block} = Dict(
diff --git a/src/setup_topology.jl b/src/setup_topology.jl
index 0874630..1778b43 100644
--- a/src/setup_topology.jl
+++ b/src/setup_topology.jl
@@ -55,8 +55,6 @@ function EnergySystemDesign(
     # Create an iterator for the current system
     elements = get_children(system)
 
-    visible::Observable{Bool} = Observable(level <= 1)
-
     design = EnergySystemDesign(
         system,
         id_to_color_map,
@@ -69,7 +67,7 @@ function EnergySystemDesign(
         Observable(BLACK),
         Observable(:E),
         file,
-        visible,
+        Observable(level == 0),
     )
 
     # If system contains any components (i.e. !isnothing(elements)) add all components
@@ -139,7 +137,7 @@ function EnergySystemDesign(
             if !isnothing(from) && !isnothing(to)
                 push!(
                     design.connections,
-                    Connection(from, to, element, id_to_color_map, Observable(level == 0)),
+                    Connection(from, to, element, design, id_to_color_map),
                 )
             end
         end
diff --git a/src/utils_GUI/GUI_utils.jl b/src/utils_GUI/GUI_utils.jl
index 575a931..4f77b7d 100644
--- a/src/utils_GUI/GUI_utils.jl
+++ b/src/utils_GUI/GUI_utils.jl
@@ -23,13 +23,22 @@ function toggle_selection_color!(gui::GUI, selection::Connection, selected::Bool
     else
         colors = get_colors(selection)
         no_colors = length(colors)
+        simplified = get_simplified(selection)[]
         i::Int64 = 1
         for plot ∈ plots
-            if isa(plot.color[], Vector)
-                plot.color = colors
+            if simplified
+                if isa(plot.color[], Vector)
+                    plot.color = [BLACK]
+                else
+                    plot.color = BLACK
+                end
             else
-                plot.color = colors[((i-1)%no_colors)+1]
-                i += 1
+                if isa(plot.color[], Vector)
+                    plot.color = colors
+                else
+                    plot.color = colors[((i-1)%no_colors)+1]
+                    i += 1
+                end
             end
         end
     end
diff --git a/src/utils_GUI/event_functions.jl b/src/utils_GUI/event_functions.jl
index b576e69..1532c54 100644
--- a/src/utils_GUI/event_functions.jl
+++ b/src/utils_GUI/event_functions.jl
@@ -11,6 +11,7 @@ function define_event_functions(gui::GUI)
 
     expand_all_toggle = get_toggle(gui, :expand_all)
     expand_all = get_var(gui, :expand_all)
+    simplified_toggle = get_toggle(gui, :simplified)
 
     # On zooming, make sure all graphics are adjusted acordingly
     on(ax_topo.finallimits; priority = 10) do finallimits
@@ -220,19 +221,19 @@ function define_event_functions(gui::GUI)
     end
 
     # Align horizontally button: Handle click on the align horizontal button
-    on(get_button(gui, :align_horizontal).clicks; priority = 10) do clicks
+    on(get_button(gui, :align_horizontal).clicks; priority = 10) do _
         align(gui, :horizontal)
         return Consume(false)
     end
 
     # Align vertically button: Handle click on the align vertical button
-    on(get_button(gui, :align_vertical).clicks; priority = 10) do clicks
+    on(get_button(gui, :align_vertical).clicks; priority = 10) do _
         align(gui, :vertical)
         return Consume(false)
     end
 
     # Open button: Handle click on the open button (open a sub system)
-    on(get_button(gui, :open).clicks; priority = 10) do clicks
+    on(get_button(gui, :open).clicks; priority = 10) do _
         if !isempty(get_selected_systems(gui))
             get_vars(gui)[:expand_all] = false
             component = get_selected_systems(gui)[end] # Choose the last selected node
@@ -243,10 +244,11 @@ function define_event_functions(gui::GUI)
                     visible = false,
                     expand_all,
                 )
-                if isa(component, EnergySystemDesign) && sub_plots_empty(component)
+                if sub_plots_empty(component)
                     initialize_plot!(gui, component)
                 end
                 gui.design = component
+                simplified_toggle.active[] = get_simplified(component)[]
                 plot_design!(
                     gui,
                     get_design(gui);
@@ -262,11 +264,12 @@ function define_event_functions(gui::GUI)
     end
 
     # Navigate up button: Handle click on the navigate up button (go back to the root_design)
-    on(get_button(gui, :up).clicks; priority = 10) do clicks
+    on(get_button(gui, :up).clicks; priority = 10) do _
         if !isa(get_parent(get_system(gui)), NothingElement)
             get_vars(gui)[:expand_all] = expand_all_toggle.active[]
             plot_design!(gui, get_design(gui); visible = false, expand_all)
             gui.design = get_root_design(gui)
+            simplified_toggle.active[] = get_simplified(get_design(gui))[]
             plot_design!(gui, get_design(gui); visible = true, expand_all)
             update_title!(gui)
             adjust_limits!(gui)
@@ -351,14 +354,21 @@ function define_event_functions(gui::GUI)
         return Consume(false)
     end
 
+    # Toggle simplified connection plotting
+    on(simplified_toggle.active; priority = 10) do val
+        design = get_design(gui)
+        toggle_simplified!(gui, design, val)
+        return Consume(false)
+    end
+
     # Save button: Handle click on the save button (save the altered coordinates)
-    on(get_button(gui, :save).clicks; priority = 10) do clicks
+    on(get_button(gui, :save).clicks; priority = 10) do _
         save_design(get_design(gui))
         return Consume(false)
     end
 
     # Reset button: Reset view to the original view
-    on(get_button(gui, :reset_view).clicks; priority = 10) do clicks
+    on(get_button(gui, :reset_view).clicks; priority = 10) do _
         adjust_limits!(gui)
         notify(ax_topo.finallimits)
         return Consume(false)
diff --git a/src/utils_GUI/topo_axis_utils.jl b/src/utils_GUI/topo_axis_utils.jl
index a698493..989ca93 100644
--- a/src/utils_GUI/topo_axis_utils.jl
+++ b/src/utils_GUI/topo_axis_utils.jl
@@ -20,6 +20,15 @@ function pixel_to_data(gui::GUI, pixel_size::Real)
     return Point2f(pixel_size * x_factor, pixel_size * y_factor)
 end
 
+"""
+    data_to_pixel(gui::GUI, data_size::Real)
+
+Convert `data_size` (in x- and y-direction) to pixel sizes in design object `gui`.
+"""
+function data_to_pixel(gui::GUI, data_size::Real)
+    return data_size / l2_norm(pixel_to_data(gui, 1.0))
+end
+
 """
     update_distances!(gui::GUI)
 
@@ -124,6 +133,9 @@ Initialize the plot of the topology of design object `gui` given an EnergySystem
 `design`.
 """
 function initialize_plot!(gui::GUI, design::EnergySystemDesign)
+    simplified = get_var(gui, :simplified_connection_plotting)
+    simplify = get_var(gui, :simplify_all_levels) || (design == get_root_design(gui))
+    get_simplified(design)[] = simplified && simplify
     for component ∈ get_components(design)
         if get_var(gui, :pre_plot_sub_components)
             initialize_plot!(gui, component)
@@ -151,9 +163,26 @@ function plot_design!(
     if get_design(gui) == design
         update_distances!(gui)
     end
-    components_and_connections = vcat(get_components(design), get_connections(design))
-    for component ∈ components_and_connections
-        component.visible[] = visible
+    get_visible(design)[] = visible
+end
+
+"""
+    toggle_simplified!(gui::GUI, design::EnergySystemDesign, val::Bool)
+
+Toggle simplified connection plotting for EnergySystemDesign `design` in GUI `gui`.
+"""
+function toggle_simplified!(gui::GUI, design::EnergySystemDesign, val::Bool)
+    get_vars(gui)[:simplified_connection_plotting] = val
+    clear_selection!(gui, :topo)
+    get_simplified(design)[] = val
+    connections = get_connections(design)
+    if !isempty(connections) && isempty(get_plots(connections[1], val)) # create alternative plots
+        connect!(gui, design)
+    end
+    if get_vars(gui)[:expand_all]
+        for component ∈ get_components(design)
+            toggle_simplified!(gui, component, val)
+        end
     end
 end
 
@@ -187,8 +216,22 @@ end
 When a boolean argument `two_way` is specified, draw the lines in both directions.
 """
 function connect!(gui::GUI, connection::Connection, two_way::Bool)
-    colors = get_colors(connection)
-    no_colors = length(colors)
+    linestyles = get_linestyle(gui, connection)
+    simplified = get_simplified(connection)
+    parent = get_parent(connection)
+    if simplified[]
+        colors = [BLACK]
+        no_colors = 1
+
+        # If any of the modes contains investments, use investment linestyle
+        inv_linestyle = get_var(gui, :investment_linestyle)
+        linestyle =
+            any(style == inv_linestyle for style ∈ linestyles) ? [inv_linestyle] : [:solid]
+    else
+        colors = get_colors(connection)
+        no_colors = length(colors)
+        linestyle = linestyles
+    end
 
     # Create an arrow to highlight the direction of the energy flow
     l::Float32 = 1.0f0 # length of the arrow
@@ -204,20 +247,18 @@ function connect!(gui::GUI, connection::Connection, two_way::Bool)
     end
 
     # Allocate and store objects
-    linestyle = get_linestyle(gui, connection)
     linewidth = get_var(gui, :connection_linewidth)
-    markersize = get_var(gui, :markersize)
-    two_way_sep_px = get_var(gui, :two_way_sep_px)
     line_sep_px = get_var(gui, :line_sep_px)
     parent_scaling = get_var(gui, :parent_scaling)
+    marker_to_box_ratio = get_var(gui, :marker_to_box_ratio)
 
-    from_xy = connection.from.xy
-    to_xy = connection.to.xy
+    from_xy = get_xy(get_from(connection))
+    to_xy = get_xy(get_to(connection))
     Δh = get_var(gui, :Δh)
 
     triple = @lift begin
         pts_lines = Vector{Vector{Point2f}}(fill(fill(Point2f(0.0f0, 0.0f0), 2), no_colors))
-        markersize_length::Float32 = l2_norm(pixel_to_data(gui, markersize))
+        markersize_length::Float32 = marker_to_box_ratio * $Δh
         linewidth_length::Float32 = l2_norm(pixel_to_data(gui, linewidth))
 
         xy_1::Point2f = $from_xy
@@ -234,13 +275,13 @@ function connect!(gui::GUI, connection::Connection, two_way::Bool)
         dirθ::Point2f = Point2f(cosθ, sinθ)
 
         Δ::Float32 = $Δh / 2 # half width of a box
-        if !isempty(get_components(connection.from))
+        if !isempty(get_components(get_from(connection)))
             Δ *= parent_scaling
         end
         Δ += linewidth_length / 2
         lines_shift::Point2f =
             (linewidth_length + l2_norm(pixel_to_data(gui, line_sep_px))) * dirϕ
-        two_way_sep::Point2f = l2_norm(pixel_to_data(gui, two_way_sep_px)) * dirϕ
+        two_way_sep::Point2f = Δ / 2 * dirϕ
         xy_midpoint::Point2f = xy_2 + (no_colors - 1) / 2 * lines_shift
         if two_way # separate the opposite directed lines by two_way_sep
             xy_midpoint += two_way_sep / 2
@@ -274,6 +315,10 @@ function connect!(gui::GUI, connection::Connection, two_way::Bool)
     θs = @lift fill($triple[2], no_colors)
 
     ax = get_ax(gui, :topo)
+    visible = get_visible(parent)
+    simplified_initial::Bool = simplified[]
+    visible_plot = @lift $visible && ($simplified == simplified_initial)
+    markersize = @lift data_to_pixel(gui, marker_to_box_ratio * $Δh)
     sctr = scatter!(
         ax,
         xy_midpoints;
@@ -283,7 +328,7 @@ function connect!(gui::GUI, connection::Connection, two_way::Bool)
         color = colors,
         inspectable = false,
         depth_shift = get_var(gui, :depth_shift_lines),
-        visible = get_visible(connection),
+        visible = visible_plot,
     )
     sctr.kw[:EMGUI_obj] = connection
     push!(get_plots(connection), sctr)
@@ -299,7 +344,7 @@ function connect!(gui::GUI, connection::Connection, two_way::Bool)
             inspector_label = (self, i, p) -> get_hover_string(connection),
             inspectable = true,
             depth_shift = get_var(gui, :depth_shift_lines),
-            visible = get_visible(connection),
+            visible = visible_plot,
         )
         lns.kw[:EMGUI_obj] = connection
         push!(get_plots(connection), lns)
@@ -329,7 +374,7 @@ get_linestyle(gui::GUI, design::EnergySystemDesign) = get_linestyle(gui, design.
 function get_linestyle(gui::GUI, system::AbstractSystem)
     node = get_parent(system)
     if isa(node, EMB.Node) && EMI.has_investment(node)
-        return get_var(gui, :investment_lineStyle)
+        return get_var(gui, :investment_linestyle)
     end
     return :solid
 end
@@ -349,11 +394,11 @@ function get_linestyle(gui::GUI, connection::Connection)
     # For Links, simply use dashed style if from or to node has investments
     no_lines = length(get_colors(connection))
     linestyle::Union{Symbol,Makie.Linestyle} = get_linestyle(gui, connection.from)
-    if linestyle == get_var(gui, :investment_lineStyle)
+    if linestyle == get_var(gui, :investment_linestyle)
         return fill(linestyle, no_lines)
     end
     linestyle = get_linestyle(gui, connection.to)
-    if linestyle == get_var(gui, :investment_lineStyle)
+    if linestyle == get_var(gui, :investment_linestyle)
         return fill(linestyle, no_lines)
     end
     return fill(:solid, no_lines)
@@ -397,7 +442,7 @@ function draw_box!(gui::GUI, design::EnergySystemDesign)
             linestyle = linestyle,
             depth_shift = get_var(gui, :depth_shift_components),
             stroke_depth_shift = get_var(gui, :depth_shift_components) - 1.0f-5,
-            visible = get_visible(design),
+            visible = get_visible(get_parent(design)),
         ) # Create a white background rectangle to hide lines from connections
 
         add_inspector_to_poly!(white_rect2, (self, i, p) -> get_hover_string(design))
@@ -419,7 +464,7 @@ function draw_box!(gui::GUI, design::EnergySystemDesign)
         linestyle = linestyle,
         depth_shift = get_var(gui, :depth_shift_components),
         stroke_depth_shift = get_var(gui, :depth_shift_components) - 1.0f-5,
-        visible = get_visible(design),
+        visible = get_visible(get_parent(design)),
     ) # Create a white background rectangle to hide lines from connections
 
     add_inspector_to_poly!(white_rect, (self, i, p) -> get_hover_string(design))
@@ -502,7 +547,7 @@ function draw_icon!(gui::GUI, design::EnergySystemDesign)
             inspectable = true,
             depth_shift = get_var(gui, :depth_shift_components),
             stroke_depth_shift = get_var(gui, :depth_shift_components) - 1.0f-5,
-            visible = get_visible(design),
+            visible = get_visible(get_parent(design)),
         )
         add_inspector_to_poly!(polys, (self, i, p) -> get_hover_string(design))
         polys.kw[:EMGUI_obj] = design
@@ -525,7 +570,7 @@ function draw_icon!(gui::GUI, design::EnergySystemDesign)
                 strokewidth = get_var(gui, :linewidth),
                 depth_shift = get_var(gui, :depth_shift_components),
                 stroke_depth_shift = get_var(gui, :depth_shift_components) - 1.0f-5,
-                visible = get_visible(design),
+                visible = get_visible(get_parent(design)),
             )
 
             add_inspector_to_poly!(
@@ -549,7 +594,7 @@ function draw_icon!(gui::GUI, design::EnergySystemDesign)
             inspectable = true,
             inspector_label = (self, i, p) -> get_hover_string(design),
             depth_shift = get_var(gui, :depth_shift_components),
-            visible = get_visible(design),
+            visible = get_visible(get_parent(design)),
         )
         icon_image.kw[:EMGUI_obj] = design
         push!(get_plots(design), icon_image)
@@ -630,7 +675,7 @@ function draw_label!(gui::GUI, component::EnergySystemDesign)
         inspectable = false,
         color = has_invested(component) ? RED : BLACK,
         depth_shift = get_var(gui, :depth_shift_components),
-        visible = get_visible(component),
+        visible = get_visible(get_parent(component)),
     )
     label_text.kw[:EMGUI_obj] = component
     push!(get_plots(component), label_text)
diff --git a/test/EMI_geography_2.jl b/test/EMI_geography_2.jl
index 1842406..75c5ed3 100644
--- a/test/EMI_geography_2.jl
+++ b/test/EMI_geography_2.jl
@@ -279,6 +279,8 @@ function run_case_EMI_geography_2()
         scale_tot_opex = true,
         scale_tot_capex = false,
         pre_plot_sub_components = false,
+        simplified_connection_plotting = true,
+        simplify_all_levels = true,
     )
 
     return case, model, m, gui
diff --git a/test/test_interactivity.jl b/test/test_interactivity.jl
index e997086..b2f9500 100644
--- a/test/test_interactivity.jl
+++ b/test/test_interactivity.jl
@@ -1,23 +1,3 @@
-import EnergyModelsGUI:
-    get_component,
-    toggle_selection_color!,
-    get_plots,
-    get_selection_color,
-    get_selected_systems,
-    get_selected_plots,
-    get_visible_data,
-    get_var,
-    get_xy,
-    get_toggle,
-    get_ax,
-    update_info_box!,
-    update_available_data_menu!,
-    update_sub_system_locations!,
-    get_design,
-    get_vis_plots,
-    get_plotted_data,
-    select_data!
-
 # Load case 7 for testing
 case, model, m, gui = run_case()
 
@@ -39,6 +19,9 @@ axes_menu = get_menu(gui, :axes)
 
 pin_plot_button = get_button(gui, :pin_plot)
 
+expand_all_toggle = get_toggle(gui, :expand_all)
+simplified_toggle = get_toggle(gui, :simplified)
+
 # Test specific GUI functionalities
 @testset "Test interactivity" verbose = true begin
     op_cost = [3371970.00359, 5382390.00598, 2010420.00219]
@@ -64,27 +47,92 @@ pin_plot_button = get_button(gui, :pin_plot)
     @testset "get_toggle(gui,:expand_all).active" begin
         # Check that sub-components are initially not plotted (as pre_plot_sub_components = false)
         @test all(isempty(get_plots(component)) for component ∈ get_components(area1))
-        get_toggle(gui, :expand_all).active = true
+        expand_all_toggle.active = true
 
         # Test if node n_El 1 became invisible
-        get_toggle(gui, :expand_all).active = false
+        expand_all_toggle.active = false
         n_el_1 = get_component(area1, "El 1") # fetch the n_El 1 node
 
         # Test if node n_El 1 became invisible
         @test !get_plots(n_el_1)[1].visible[]
 
         # Test if node n_El 1 became visible again
-        get_toggle(gui, :expand_all).active = true
+        expand_all_toggle.active = true
         @test get_plots(n_el_1)[1].visible[]
 
         # Check that that sub-components are now plotted
         @test all(!isempty(get_plots(component)) for component ∈ get_components(area1))
     end
 
+    # Test simplified toggle functionality
+    @testset "get_toggle(gui,:simplified).active" begin
+        # Check that simplified plots are initially not plotted
+        @test all(isempty(get_simplified_plots(connection)) for connection ∈ connections)
+        @test all(
+            isempty(get_simplified_plots(connection)) for component ∈ components for
+            connection ∈ get_connections(component)
+        )
+
+        # Also check that all colors are regular colors
+        test_all_connection_colors(gui, :regular_colors)
+
+        # Activate simplified view (for expanded view - simplified for all levels)
+        simplified_toggle.active = true
+        test_all_connection_colors(gui, :black)
+
+        # Deactivate simplified view
+        simplified_toggle.active = false
+        test_all_connection_colors(gui, :regular_colors)
+
+        # deexpand
+        expand_all_toggle.active = false
+        pick_component!(gui, connections[1], :topo)
+        update!(gui)
+        simplified_toggle.active = true
+
+        # Check that simplified plots are used only on the current level
+        test_connections_colors(gui, connections, :black)
+        test_connections_colors(gui, components, :regular_colors)
+
+        pick_component!(gui, area1, :topo)
+        notify(get_button(gui, :open).clicks)
+        test_connections_colors(gui, get_connections(area1), :regular_colors)
+        simplified_toggle.active = true
+        test_connections_colors(gui, get_connections(area1), :black)
+
+        # Test that the previous toggling did not affect other areas
+        for area ∈ [area2, area3, area4]
+            notify(get_button(gui, :up).clicks)
+            pick_component!(gui, area, :topo)
+            notify(get_button(gui, :open).clicks)
+            test_connections_colors(gui, get_connections(area), :regular_colors)
+            update!(gui)
+        end
+    end
+
+    _, _, _, gui_2 = run_case_EMI_geography_2()
+    design_2 = get_root_design(gui_2)
+    components_2 = get_components(design_2)
+    connections_2 = get_connections(design_2)
+    simplified_toggle_2 = get_toggle(gui_2, :simplified)
+
+    # Test simplify_all_levels=true functionality
+    @testset "Test simplify_all_levels=true functionality" begin
+        # Check that simplified plots are used on all levels
+        test_all_connection_colors(gui_2, :black)
+        for area ∈ components_2
+            pick_component!(gui_2, area, :topo)
+            notify(get_button(gui_2, :open).clicks)
+            test_connections_colors(gui_2, get_connections(area), :black)
+            simplified_toggle_2.active = false
+            test_connections_colors(gui_2, get_connections(area), :regular_colors)
+            notify(get_button(gui_2, :up).clicks)
+        end
+        simplified_toggle_2.active = false
+    end
+
     # Test color toggling
     @testset "Toggle colors" begin
-        _, _, _, gui_2 = run_case_EMI_geography_2()
-        design_2 = get_root_design(gui_2)
         oslo = get_component(design_2, 1)
         pick_component!(gui_2, get_plots(oslo)[1], :topo)
         update!(gui_2)
@@ -103,24 +151,12 @@ pin_plot_button = get_button(gui, :pin_plot)
         notify(get_button(gui_2, :up).clicks) # Go back to the top level
 
         connection1 = get_connections(design_2)[5] # fetch the Oslo - Trondheim transmission
-        plt_connection1 = get_plots(connection1)
-        pick_component!(gui_2, plt_connection1[2], :topo)
+        pick_component!(gui_2, get_plots(connection1)[2], :topo)
         update!(gui_2)
-        @test all(
-            all(plot.color[] .== get_selection_color(gui_2)) for plot ∈ plt_connection1
-        )
+        test_connection_colors(gui_2, connection1, :selection_color)
         pick_component!(gui_2, nothing, :topo) # deselect
         update!(gui_2)
-        i::Int64 = 1
-        no_colors::Int64 = length(connection1.colors)
-        for plot ∈ plt_connection1
-            if isa(plot.color[], Vector)
-                @test plot.color[] == connection1.colors
-            else
-                @test plot.color[] == connection1.colors[((i-1)%no_colors)+1]
-                i += 1
-            end
-        end
+        test_connection_colors(gui_2, connection1, :regular_colors)
     end
 
     # Test the open button functionality
@@ -315,6 +351,8 @@ pin_plot_button = get_button(gui, :pin_plot)
         "Topo" => ["svg", "lp", "mps"],
     )
     @testset "get_button(gui,:export).clicks" begin
+        tmpdir = mktempdir(testdir; prefix = "exported_files_")
+        get_vars(gui)[:path_to_results] = tmpdir
         path = get_var(gui, :path_to_results)
 
         # Loop through all combinations of export options
diff --git a/test/utils.jl b/test/utils.jl
index 0b2210d..1054aa8 100644
--- a/test/utils.jl
+++ b/test/utils.jl
@@ -1,12 +1,36 @@
 import EnergyModelsGUI:
     get_root_design,
+    get_component,
     get_components,
     get_connections,
+    get_selection_color,
+    get_ref_element,
+    get_element,
     get_menu,
     get_button,
     update!,
+    BLACK,
+    Connection,
     pick_component!,
-    clear_selection!
+    clear_selection!,
+    toggle_selection_color!,
+    get_plots,
+    get_selected_systems,
+    get_selected_plots,
+    get_visible_data,
+    get_simplified_plots,
+    get_vars,
+    get_var,
+    get_xy,
+    get_toggle,
+    get_ax,
+    update_info_box!,
+    update_available_data_menu!,
+    update_sub_system_locations!,
+    get_design,
+    get_vis_plots,
+    get_plotted_data,
+    select_data!
 
 """
     run_through_all(gui::GUI)
@@ -99,3 +123,52 @@ function run_through_menu(
         end
     end
 end
+
+function test_connection_colors(gui::GUI, connection::Connection, type::Symbol)
+    plt_connection = get_plots(connection)
+    if type == :black || type == :selection_color
+        expected_color = type == :black ? BLACK : get_selection_color(gui)
+
+        @test all(
+            all(plot.color[] .== expected_color) for plot ∈ plt_connection
+        )
+    elseif type == :regular_colors
+        i::Int64 = 1
+        no_colors::Int64 = length(connection.colors)
+        for plot ∈ plt_connection
+            if isa(plot.color[], Vector)
+                @test plot.color[] == connection.colors
+            else
+                @test plot.color[] == connection.colors[((i-1)%no_colors)+1]
+                i += 1
+            end
+        end
+    end
+end
+
+function test_connections_colors(gui::GUI, connections::Vector{Connection}, type::Symbol)
+    for connection ∈ connections
+        test_connection_colors(gui, connection, type)
+    end
+end
+
+function test_connections_colors(
+    gui::GUI,
+    components::Vector{EnergySystemDesign},
+    type::Symbol,
+)
+    for component ∈ components
+        test_connections_colors(gui, get_connections(component), type)
+    end
+end
+
+function test_all_connection_colors(gui::GUI, type::Symbol)
+    design = get_root_design(gui)
+    components = get_components(design)
+    connections = get_connections(design)
+
+    test_connections_colors(gui, connections, type)
+    for component ∈ components
+        test_connections_colors(gui, get_connections(component), type)
+    end
+end