This turns off the Windows built in Win+S shortcut (removing it from Cortana), additionally a value of "SR" for instance would also disable Win+R (run).
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced] "DisabledHotkeys"="S"
After setting this registry key restart Windows and Win+S will work for OneNote again.
I'm not really sure why so many people who don't know the actual answer to a question still choose to chime in, it's kind of frustrating how often I end up on Stack Exchange these days only to discover that people are providing misinformation or useless conjecture.