I’ve often wondered that, too. Even little things like dying one’s hair, putting on makeup, wearing a toupee, even dressing to hide one’s figure flaws, aren’t we saying we aren’t happy with the way God made us?
Dieting and Body Building should also be added to that list...
I would say all the above fit under the Sin of “Vanity”, however, it is a sin like Gluttony as well..
Forgivable, but one is supposed to try not to do it as much...
Wanting to appear different externally could have reasons that are based in honest glorification of God. But not a mutilation or costuming to appear a different gender. That’s based in the hatred that comes from hell, and as I said, hell’s hatred can be very pleasurable at least until the heaven still in you rebels.