Adding to the DV_QUANTITY units options

As part of an ongoing project at Region Östergötland ( Cardiology templates and archetypes - #14 by davwet ) we are creating a new archetype for echocardiography including measurements set by clinicians. These include some values divided by body surface area (BSA) which are given the unit mm/(m^2), but this unit does not exist in Archetype Designer right now. Is it possible to get some help with adding this unit, or perhaps an option for {LENGTH/AREA}?