Not sure where to bring this suggestion up so I’m dropping it here.
When clicking on a folder’s share icon to get the sharing drop-down menu, adding an option “Prohibit Sharing” requiring an admin password to uncheck would be helpful. I prepare income tax returns and use Nextcloud (love it!!) as a client portal where we are able to share documents back and forth, including completed tax returns. Mistakenly sharing certain folders with individuals or groups would be catastrophic, for example my top-level 2020 Tax folder inside of which are all my individual client folders. This folder must never be shared so adding a “Prohibit Sharing” option would provide an added safety measure.
It also should never be allowed to be inadvertently dragged into another folder, but perhaps that’s for another thread.