I've found the new location for the Dropbox folder on MacOS, in my case: /Users/****/Library/CloudStorage/Dropbox.
But, trying to drag and drop this folder into the Finder favourites does nothing. This used to work, and I used to have this folder in the favourites. How can you re-add the folder to the favourites?
(In fact, I tried to drag this item from the favourites into a terminal session to paste the folder's location in the terminal, and not only did this not work, but the favourite was removed from finder.)
I don't understand why the Dropbox folder works differently from every other folder in MacOS, the new setup seems like a huge step backward. When navigating to the folder in Finder, the "up one directory" keyboard command (cmd + up arrow) doesn't work, and you also can't use the "right click on folder name" system to see its parent folders like you can do with other folders. And the folder is much harder to find than it used to be, now that it's buried in this hidden Library folder instead of just being in the home folder.