A family of Microsoft products that enable users to capture, organize, and reuse notes electronically.
Exactly the same problem.
Evidently someone who never uses oneNote on a regular basis decided to change the layout without actually asking real users - again.
Put it back where it was. It now takes up note space and for those of use that use the multi column/free format oneNote is so good at it causes information to be hidden.
It is not conent so it should NOT/NEVER EVER etc be part of the content pane