Are you talking about the Skyrim mod? It’s highly advised against to manually install that mod unless you create a backup of your game first and you know what you’re doing, which I don’t. Unless you can get vortex or mo2 up and running. Heres a good video on how. Be warned though , I tried to use vortex around 6 months ago and it broke everything after a steam deck is update. He has a more recent video though that should work. https://youtu.be/kpoHTvJmw-o?si=wUMWdrDsSYYntSr1

You can also just use the in-game mods from choosing mods on the main menu. There’s a reddit thread on “lazy mod list for Skyrim on the steam deck” if you google it. But it doesn’t include race menu that I know of.