Prevent map to become dark when opening a dialog window

When I open the dialog "fast map changer" I can still see 2/3 of the current map. The same happens when I open the dialog to control the transparency for a map overlay.

At same time the dialog opens, the still visible map is shaded darker ("goes into the background").

It would be very nice if this darkening could be disabled when opening dialogs that do not use the complete screen.

This would make the control of transparency etc. much more easier!

Is this maybe already possible by some kind of setting?