Welcome, you amazing community of The Amazing Game, especially you Wube Software lads!
So I haven't been following the amazing game for a year or so; only downloading latest update every few months but not the forum, so some suggestions are already or to some extent implemented, at least in some mod.
TL;DR
Add shortcut for setting BP Book's active BPI suggest alt+<some mouse button> or middle mouse button, instead of scrolling mouse wheel (unless I'm not up to date with controls).