Building: select which materials to use

Sometimes when you're building stuff, especially with Aid missions, you build a tent or a bedroll and you don't get to select whether you insert the wood or fibre you picked up around the Aid area specifically for this, or the rare fibre/wood you've been collecting elsewhere in the realm. We need a setting where we can select which materials it uses from our inventory, otherwise we have to drop our rare stuff on the ground while doing Aid missions.