Hi, all,
What do you think about creating a firefox-about:config-like interface for the hidden preferences? For example, a "Various" tab in the preferences dialog, with a "name value" list, a check button or a text entry (depending on the currenttly selected element), and a link to www.geany.org/manual/current/#hidden-preferences.
That'll take some time to write, for example to check that all changes are applied immediately, but I'm willing to do it, if you think it's a good idea. The stash provides a good base for such an interface.