Adding a discount code to the processing screen

Whilst we can now add discount codes to online bookings, when running ads/promotions, could we add a box on the processing screen that picks up a current discount code already set up? I know we can start doing maths and changing amount owing etc but apart from it decreasing errors, it would be nice to then be able to track how many codes have been used across the platform etc to see which have been more successful etc.