If I have to pick something, I’d say the thumb clusters. I barely use the top ones in the center because they’re a bit of an awkward reach for my hand size. The bottom ones on the outside are also weird because you’d need to do some finger curl or move your hands. I just ended up mapping the keys I don’t use as much over there and it hasn’t been an issue, but it is some wasted potential :)

Missing the keyboard smash and the xyz_final_final