Marginnote Mac App syncs with Documents folder, not iCloud/Marginnote folder

Marginnote on my Mac syncs with the documents folder, not the iCloud/MarginNote 3 folder (which my iPad happily uses).

This makes using MarginNote on my Mac pretty much unusable (actually dangerous, because of MN’s tendency to sometimes delete data…).

How can I change the sync folder location to the iCloud/MarginNote 3 folder?