• If you want to "transfer" a folder, simply share it with the other account. The other account can save the folder in its own folders.
• If the maps in the folder should really pass into the ownership of the other account, that account copies the maps individually (Case 2) and places them in its own folder.

For many maps, the folder is the easiest handover: the previous owner shares the folder, the new account gradually copies what it really needs.