I used to have my Documents folder symlinked into my Dropbox to allow it to back up automatically. Since symlinks aren’t supported anymore, and since I am in the middle of setting up a new computer I thought I would try to fix this the recommended way - putting my actual documents in the Dropbox folder and symlinking back to the Documents folder.
This seems to be ok, but every time I reboot the symlink is gone and my documents folder just appears empty.
Hmm. Since you mention that you're renaming the Documents folder, if this is one of the OS's default folders, could you revert it back to its original name and then reboot? Maybe that will do the trick.
If I rename the original Documents folder back to Documents, then I can't make the alias as there's already a ~/Documents that exists. It appears that when I reboot Catalina is noticing that there is no ~/Documents, and creating one.
I messed around with it for awhile, and I believe I may have solved it. It's survived a reboot at least. I do need to get the original ~/Documents out of the way. But instead of creating the link on the command line, when I did it in Finder (right click, "Create Alias", then move it to ~/ it seems to have held.