In pro audio applications like Wavelab bookmarking is very advanced. Of this one solution would greatly benefit audiobook listeners on Rockbox.
The distinction permanent vs temporary bookmark.
Normally, bookmarks can greatly simplify our lives by marking the last playback position, especially with several long audiobooks listened to in turns.
But you may no longer need such a bookmark which has already been updated by a newer one as you progress. These bookmarks I would call temporary. Thus, upon stopping playback, by default a temporary might be placed.
Still, those moments which seem worth remembering or listening to again at a later time can easily be confused with those, when we simply interrupted listening.
Enter permanent markers.
Thus Context Menu>Bookmarks could look as follows:
Create temporary bookmark
Create Permanent bookmark
List all bookmarks
List temporary bookmarks
List permanent bookmarks
Upon entering List permanent bookmarks another option might be present: "rename", so that you might give the permanent bookmarks their optional unique names.