Just press Shift + F12 to disable it in the menus. Though, unless you go into Options > Screen and bind Shift + F12 to your current resolution, there's a chance LFS might change it. So, go into Options, Screen, over on the right, click the button that says "F12", then, Shift + F12 will only disable the mod, so you can use the menu. Shift + F12 will also enable it again, when you get into the game.