In OneNote for windows, heading style can be changed by pressing Ctrl + Alt + [number].
The issue:
Several keyboard setups (e.g. Norwegian) have three available symbols on the number keys.
Pressing "AltGr + 2" gives @, and pressing "AltGr + 3" gives £.
The annoying thing is that in Onenote for Windows the shortcut "Ctrl + Alt + 2" will also insert an @ symbol, in addition to changing the headline. This was not an issue in OneNote 2016, as that was set up to only accept AltGr button, and not Ctrl+Alt to input the symbol.
How to reproduce bug:
Change keyboard setup to Norwegian, and use shortcut Ctrl+Alt+2 to change style to heading 2 on some text.
Suggested bug-fix:
Only accept AltGr button as modifier for selecting symbols on the numbers (and not Ctrl + Alt).