OneDrive folder keeps moving to bottom of Finder Favorites sidebar
This was bugging me as well, until I noticed one of my Macs didn't move it to the bottom. The difference? On that Mac, OneDrive was installed via the App Store, whereas the others were downloaded from the OneDrive web site. 

So I uninstalled OneDrive from those affected Macs, reinstalled it from the App Store, and made sure I re-enabled the Finder Extension. Now after a restart, the OneDrive folder stays where I placed it in the Favorites side bar! :)