Impossible to create a single natural chord
There is no way to add a single natural as an indication of a chord.
You can have anything natural (ABCDEFG etc.) but not a natural by itself.
It's needed notably in ancient music and in reduced chord notation.
Apart from that, it would be nice to have a consistent keyboard layout to enter accidentals (you have # for sharp, b for bemol in certain cases and nothing for natural) anywhere in MS (note entry, chord entry, alteration of turns, etc.)