I did it as I went along.
I moved a batch (~20) of books to my TBA (to be added) folder (was before Auto Add folder

)
Added the books, resolved issues, moved AGAIN to my Archive (if not the trash)
Repeat
Now there is the
Auto Add folder option (see the tab on preferences:ADDING BOOKS)
Books placed there get added, then they auto-move to trash.

stuff left behind, did not add. you need to figure out why or delete