I think a user selectable button would be the best option, because I suspect everyone probably holds their nit a little bit differently. Short of that I agree that if a single button must be hard coded as a modifier, it should be one that all three nits have in common.

However, Just in case my tone comes across otherwise, I want to make clear that I don't think I have any more say in the matter than any other user. My intention was just to get an itch scratched that I couldn't scratch for myself. I am grateful for your work.