It would be nice if I could, say, rename a tag. So, for example, if I had a tag named "map", I'd like to be able to rename it to "maps" and have all bookmarks with that tag updated. Same with deleting a tag from all the bookmarks that have it.
I'd like to be able to:
- see a list of all my tags, in various sort orders, and be able to navigate through them like folders (expanding and collapsing their contents).
- perform operations on the bookmarks with a certain tag. For instance, to be able to take a certain subset of them and move them to another tag, again much like what was possible with folders.
- make comments on tags that include a full markup language (org-mode markup ideally, but some regular markup would be better than just vanilla ascii).
That's just off the top of my head. There have been other features which I've wished for over the years that Firefox's bookmark manager didn't have but I knew I could easily get with org-mode in emacs.