As I repeated on #3410 till I was blue in the face, Geany blinks follow the desktop settings on Cinnamon, there is no need for a Geany setting on sensible systems, especially as the way its implemented here will disconnect Geany from the desktop settings forever.
For fruits and fenesters systems having an option in Geany's UI might make sense since their users would have to edit `settings.ini` otherwise.
So as to not need to make the presence of this option system dependent it needs an extra option to "follow the system settings" which defaults to on for Linux and off for other systems via a teeny leetle ifdef.
(Note GTK4 reads user settings from NSUserDefaults so Macos could be set to follow system again by default when we get there, but still no registry action).