I have five iPads I share with my band. All of them login with the same Apple ID, so keeping them synced is not an issue. The issue is syncing with my wife's iPad who logins with your own Apple ID. Is this possible? I don't see anywhere, where I can can login into to ST3 with different Apple ID than the one logged into on the iPad.
My workaround at the moment is to do a full backup from my iPad to my iCloud Drive, then copy the backup file to her iCloud Drive and then restore it to her iPad. Very clumsy. Lots of steps.