Only open side pane/thumbnails by default when there's multiple pages
When opening a lot of PDFs, 90% of which only contain only one page, I tend to always close the side pane with the page thumbnails to gain some screen real estate and legibility.
It'd be nice if this happened by default. So if there's >1 page, the thumbnails side pane should open, just like what happens currently. But if there's only one, it should stay closed.