Allow user to choose to display edges to invisible nodes or not

[So-Fras]

Describe the current behavior

In network-area diagrams, invisible nodes are nodes that are directly connected to the nodes displayed in the diagram. They are part of the graph but are not displayed. However, the edges towards invisible voltage levels are drawn.

For highly-connected nodes, users may want not to display those edges, in order to increase readability: However, it is not possible today.

Describe the expected behavior

Users should be able to choose whether they want to draw those edges or not.

Describe the motivation

Improve the network-area diagram customization and readability.

Extra Information

No response