I just remembered that we do actually have an alternative shortcut working. It’s not exactly the same as you are suggesting, but maybe it will work for you?
If you while inside the drawing area pane hold your Ctrl key (or Cmd key on Mac), you can drag left/right to change the size of your pen – or drag vertically, to adjust the opacity.
I hope this will help you! Please let me know. 😉
Thanks,
Niels