I often have the problem of a Control or Area2D not reacting to mouse events, because somewhere in my tree one of the stop/pass/ignore settings is wrong.
So I was wondering, if there is some tool or debug helper that would allow me to see where a given event goes, i.e. which node swallows it?
If you want to know which Control is consuming the event then try clicking on it while the game is running and check the Misc tab in the Debugger dock. Check if Last Clicked Control field shows anything. If it does, set that control Control.mouse_filter to Ignore and repeat.