Apologies if this has been posted before.
A simple option to use last formation when placing units into battle. Places the same units, if available, in the spot you put them in last battle. If they aren't available that spot is just left empty. Would make grinding encounters much faster especially if trying to rank up units regardless of encounter. I don't want to scroll back and forth to find what I need then place them all back in the same spot every battle. Would be very helpful in reducing the search for units in long unit bars on mobile.