So I have 4 panels like so, but I'd really like to combine the 2 big ones into 1. So I drag and drop them until I have only one left (BDAG), like so:

But when I drag BDAG over, it causes 2 problems: 1) Empty space not filled (and I don't know how to fill it). 2) All my books in the center panel go blank. All of 'em. Now what?
