technically, it's the mouse wheel, not the middle button.
It's probably not user configurable for the time being.
A new setting can be added for this to the development branch.
phaze14 wrote
Hey guys, just got with my engineer to start using librecad for work stuff since we ditched windows. We're liking it, but we found one hiccup that he's not getting used to, mmb for pan. He's used to doing it with rmb, is there a place to change that in settings? I tried going through all the menus and didn't find anything for button mapping. Thanks for help.