No, you don't have to recompile Geany. I'm unfortunately not familiar with how GTK works on Windows but in principle you have to place the theme (the Prof-Gnome directory I linked above) to place (1) and edit `settings.ini` at place (2) to set Prof-Gnome as the used theme. Now the question is where (1) and (2) are on Windows. For linux you can check e.g. https://wiki.archlinux.org/title/GTK