Offhand runes? I might've missed something

I feel like I probably missed something obvious here but. When I have an offhand bow equipped and I press LB it still just shows the runes for my main hand weapon? Not sure how to actually use the bow without unequipping my main hand.

Also does the same thing if I just try and use CTRL, just shows and uses my main hand runes.

Are you using a 2-handed weapon (including double daggers)?

I think that makes a difference. I’m not actually sure how to swap to my offhand in that situation, though.