That's interesting! I only knew about alt-left-click for moving from anywhere in the window. Unfortunately the middle click with my laptop's touchpad is more a "middle tap" in the corner, and it only has extra keys for left and right clicks, so I can't really hold a middle click. But it might come in handy with mice. I can also partly solve my issue if I resize in two steps, i.e. width first then length, because then I just need to grab a side and not hit and hold the corner exactly, which is harder.