You can have as many folders to "archive", and the first one will be used for "move to archive".
OK, I tried this, but which one is the "first one"? The folders are sorted alphabetically and messages seem to be moved to the second archive folder, but I want the other.
First is my real archive, set to "Archive, don't sync".
Second one (unimportant) is set to "Archive with sync" and IMAP push is enabled.