My Documents folder is in DropBox. I want it back in my Home folder.
iMac 21.5", Late 2013. High Sierra 10.13.4.
When I set up my Mac a couple of years ago I had more DropBox storage than iCloud storage so I dragged my Documents folder into DropBox, where it's been ever since.
Lately I've sprung for more iCloud storage, while I've outgrown my DropBox storage, so I'd like move the Documents folder back to the more conventional location, inside my Home folder. However when I try to drag it from DropBox to the Home folder a popup appears saying, "'Documents' can't be modified or deleted because it's required by macOS."
The system didn't have any problems with me moving it into DropBox in the first place. How can I now move it back to my Home folder?
iMac, MacBook, Mac OS X (10.5.7)