Alphabetical order for categories might make sense, but I'm not convinced it'd help much. And the categories themselves could be questioned as well.
Allowing to set a shortcut would probably be good like for everything else, but it should not get in the way by polluting the keybindings configuration -- but that could probably be easily handled.
A "top N" doesn't seem like worth the hassle to me because I don't expect this to be used often enough to improve things a lot for the user. I have to agree with @elextr that these options seem seldom used to me -- useful, yes, but not something I expect people to use every day.
I'd suggest looking at e.g. the [Commander plugin](https://plugins.geany.org/commander.html) for accessing this quickly at least in the meantime. And possibly if you're really using this very often and in a specific way, consider writing a simple plugin that would present a UI more suited to your needs.
In the end, IMO the best solution I see would to allow binding all these to shortcuts, but as @elextr would say, Somebody Has to Do It™, and it might not be totally trivial to do it right.