Organizing 60,000 folders

Creating and debugging a script to do the work could take as long as doing the move manually.  If you are familiar with regular expressions to make the file selections, then something like Total Commander can be of use.  But that is still interractive.

If you don't have space for another copy, a snapshot is also a good idea.

Note that if you are moving files to another share, not a another folder within the same share, that's another BTRFS sub-volume and it won't be a true move, it will be a copy and delete.  That will take much longer, and since the snapshopts of the old share will still contain the data, this type of "move" uses up space.  A move within a share just moves the pointer to it, not the data, so it's quick and the snapshot barely changes.