Yes, and your proposed workaround seems like a good idea. It would also work for Presets and eliminate the "Restart" button. I'll work on that and include the fix in the next version. Thanks.You seem to need to close the app and restart it before you see your new bookmarks.
I think it is a limitation of gtkdialog, although perhaps zigbert, Patriot or potong know better.I don't know of a way to refresh/(change_the_contents_of) a Combobox in a running gtkdialog. As far as I can see it doesn't allow <input></input> and then, refresh..., but maybe I'm wrong.
Cheers