Loading gamemode in singleplayer?

okay, I’ve been trying to load a gamemode in singleplayer, but I can’t figure out how to load the gamemode. All the tutorials I find are for “loading gamemodes in dedicated servers”, which I don’t have. and I’ve tried using “sv_gamemode” but it doesn’t seem to do anything either.

Isn’t there a dropdown menu on Create Game.

sv_defaultgamemode <your gamemode’s folder name>

reload map

Example:

sv_defaultgamemode sandbox

map gm_construct

On single player, go to the menu, press Create Game, click on the wrench icon, and change the gamemode you would want to run.