@MJ1 @Adrian_Joachim, thank you both for your replies! I assumed (though didn’t say - apologies) that this would have to be done at the firmware level. I’ll look into ectool for my 13 and see if it can be done. I have a 16 on order, and will definitely play with QMK when the time comes. That’s a great bit of information. If someone has already managed something like this, I look forward to your tips!
Edit: I found @Dhowett’s post on the firmware and keymap, and there he says:
That didn’t show up when I searched, because my search was too specific (about context menu, not fn key mapping generally). It looks like this one is answered, and the answer is (for now, anyway), “no.”
C’est la vie. I’ll play with the 16 when it comes, and thanks again to both of you for your hints in the right direction!