@awesomerobot, you are probably far ahead of me, but I was thinking about this this morning and wanted to put it in writing in case it’s helpful. I can think of these different types of menu items:
Internal Links
What’s there now, with usability enhancements and so on.
External Links
Probably most important for admin-configured menus — docs, legal/compliance policy links, etc.
“Watchable” Items
As many of the non-custom sections have now: selected categories, tags, inboxes, messages, chat channels, personal chats.
Might as well also add the ability to pin a particular topic. This could be bookmarks, but I would use this for a few particular posts beyond bookmarks (which I mostly use for timed reminders). For example Fedora Strategy 2028: a topic index for our planning process - Fedora Discussion.
(The difference from an internal link: it’d have an indicator of new replies or edits, and possibly a counter.)
Dynamic Watchables
Rather than particular channels, tags, topics, etc., there could be:
- most recently-active N categories
- tags that match the pattern
release-* - top 5 topics that match a search term
- most-used personal chats
… these would, I hope obviously, add multiple entries. (Possibly requiring the whole section to be for that? Maybe!)
Moderator Tools
Could duplicate the notification for the review queue (with indicator for something needing to be handled), but I’m thinking beyond that:
- last five topics from new users
- new hits for a particular watched word
- topics which are getting heated (using the Disorder plugin or other heuristics like two people replying back and forth quickly
- something indicating other mods’ recent actions?
- probably a lot more ideas…
Also, this could be where my “sudo mode” switch would go. 
User Options
Like the theme selector, but other options too. Title, status, flair, featured topic, etc.
