The one multi-window functionality I need is the ability have the iPad in portrait mode and split the screen horizontally. That way I could have a book or movie on top and notes on the bottom. It seems that iPadOS still cannot do this very basic thing. It's frustrating beyond belief knowing that this device could be so much more useful with that tiny basic functionality that has existed in GUIs for decades.

(And why on Earth does iOS allow me to split a portrait mode vertically, creating two thin strips that are seemingly useless for any work?)