Draw Decal on Floor using a Path

Hi guys, I am trying to connect two GameObjects in my scene with a Path using the A* Pathfinding package during the Editormode.

I do have a Button and a Door in my Scene, once the button is pressed, the door should open. To help the player, I want to visualize the connection between the button and the right door using a colored path on the floor. I do need it in the Editor.

Has anybody any ideas or any hints how to achiev this? I don't have any clue how to get the navmesh / astar running in EditorMode.

Has anybody done something like this?

Thanks in advance. Greets Andi