Hi
I also have a K3.
I rutinely do a backup of ALL files and folder on my K3.
Not just the documents folder.
Collections are hidden within the systems folder (collections.json)
Being a bit lazy, I just select all files and folders on my K3 when it's connected, and copy where wever I want the backup.
Might be a bit slower, but .. I have a copy of all I can.
Hope this helps as well.
Cheers,
P.S. Love your avatar