ProseMirror’s data is nested JSON also, why I can not find the example of ProseMirror + shareDB?
I know with prosemirror-collab and yjs can do it, but i really need shareDB.
I think shareDB does conflict resolution on it’s own way. My intuition is that rebasing unsynced steps won’t work when you receive shareDB diffs. I’d just go with the usual prosemirror-collab and use shareDB to send the steps to clients. But don’t bet on this answer 
anything new?