GtkTreeViews with Buttons need a unified look (inline-toolbar or not, button with icons+label or only icons, symbolic vs. colored icons, position of toolbar - horizontal vs. vertical)

GtkStackSwitcher vs. GtkNotebook (if to use GtkStackSwitcher in place of GtkNotebook and if yes, under which circumstances) - see xfce4-notifyd-config for an example of GtkStackSwitcher

On Focus and Settings tabs, some keyboard accelerators are highlighted by default. Doesn't happen when the dialog is run as standalone.