Looks really cool when it's a sword/dagger combo. It's kind of funny, but if one of the weapon types you're using doesn't 'cross-sheath' (draw from the other side of the body), you can actually have two weapons hanging from the same side. I have 5 active saves and got it to work on all five. Hopefully this isn't simply a glitch in my game.

I basically place one right-hand weapon in my inventory, and two matching left-hand weapons, then I go into Items ~ Weapons, equip the right-hand weapon and favorite it, then the trick is to make sure the two matching left-hand weapons are separated in the menu (so they don't show as Ebony Mace(2) for example), then equip one of them and favorite both, and voila! Though sometimes you may have to favorite/unfavorite and switch between which of the 2 left-hand weapons a few times until it takes, it works every time. Maybe one of you guys can try it and then explain it better. at least I can make it work every time, but I don't exactly understand how. So I sort of figured out how to dual-sheath on purpose.

Skyrim dual wield mods