Oh my god, this was so necessary. This has been requested previously, and I even tried to write some python script which is now defunct.
I'm trying to use Joplin as "Personal Knowledge Base", and once I have collected enough notes I don't remember which ones I have. The "random" button is a beautiful way to (re-) discover old notes, then review them, connect them to other notes, or move them to a more relevant folder.
Thanks a lot for this, I'm looking forward to try it out! 
(edit: Works like a charm, best thing since sliced bread!)