Solutions in order of the problems listed: https://superuser.com/questions/1927207/how-to-remove-the-st..., https://github.com/midrare/hyperenable, and my favorite: downgrade to a previous version of office which is almost certainly unsafe and has active exploits (16.0.19929.20106). But I hate that button THAT much and my wife refuses to move off of Onenote for our family knowledge management. I am close to just using Onenote in a browser (where I can zap the offending element) but the loading pages on demand is annoying.
Haters gonns hate I suppose