More generally I still don't really like/understand why we need the `$configdir/geany.css` stuff, as the only use case for it seems to style GTK stock dialogs differently inside Geany only (which seems an artificial need, but well), and that IMO it makes more sense to let user use the GTK-provided facility for that. They can always `@import` their secondary files from *~/.config/gtk-3.0/gtk.css* if they want to have nice splitting or something.