Common scenario: you want to rearm your AA piece. However, it is surrounded by transports and tanks with partially depleted ammo that will drain the supply truck in an instant. Turning off ammo resupply won’t help, since it is ammo that you want to give to the AA piece.

Or maybe you want to replenish an infantry squad without wasting supply on its half-dead 5pt transport? Regardless of the situation, the most obvious solution is to rearrange the clump so that the desired unit is in the resupply circle and the rest are not. This is cumbersome and unnecessary. With the supply truck selected, you can right click individual units you want to resupply. Only that particular unit will receive resources, even if others are in range.

Keep in mind that this does not increase repair/rearm speed. If a supply unit needs a minute to fix a tank, it can also fix five tanks in a minute – working on multiple units does not slow any individual unit’s service time, and working on a single unit does not speed things up.

Since you will be using this to avoid resupplying useless units, keep in mind that once the right-clicked unit has been fully serviced, the truck will revert to working on everything in range. You can make it automatically leave the area instead by queuing a move order with shift-right click.