Teensy Function layer?

[pixel5]

I am going to be building a custom handwired 60% soon. I'd like for it have an Fn layer that works like the Poker II's. Is this easily achievable with the Teensy?

[Charger]

I don't know how the poker is but you can set up layers to change key layout with out much work. you can set it up to change the full layout after pressed or so that you have to hold it to make fn keys like on a laptop. I have both ways set up in my keyboard layer for gaming and fn style hotkeys for volume and other things