[GtkDialog](https://developer.gnome.org/gtk3/stable/GtkDialog.html) allows you to [add "action widgets"](https://developer.gnome.org/gtk3/stable/GtkDialog.html#gtk-dialog-add-action-widget) so it would be relatively trivial to add a checkbox or combobox into it, specific to a particular application.
As for the fonts, you can use [Pango directly to get a list of all fonts](https://developer.gnome.org/pango/stable/pango-Fonts.html#pango-font-map-list-families), and it contains information about each font such as [whether they're fixed-width](https://developer.gnome.org/pango/stable/pango-Fonts.html#pango-font-family-is-monospace) or such. There's no real technical hurdles here, the only blockers are 1) who's going to write the code, and 2) is this a feature people want in Geany. -- You are receiving this because you are subscribed to this thread. Reply to this email directly or view it on GitHub: https://github.com/geany/geany/issues/1928#issuecomment-415229013
