When I have two documents open and then I hit View Side-by-side, I'd prefer that it default to putting PDF1 on Window 1 and PDF 2 on Window 2
Rather than PDF 1 and PDF 2 on Window 1, and PDF 1 on Window 2
Better yet, Side-by-side should put both PDF 1 and PDF 2 in both windows
And maybe there should be a Duplicate Tab option in case I want to quickly have three versions of PDF 1 in Window 1 or something