Log into SMS Pro. (You MAY need to be level 6 or 7) IMPORTANT: As of this writing, the reason codes MUST be entered/edited at EACH STORE, not the Host.
Open Auxiliary / Reason codes table.
Either select code to EDIT or "+" to Add new code.
IMPORTANT, Exception code MUST be correct one for location of code to appear, per this table:
ALSO, the screen button's FUNCTION must have a "REASON" paramater, such as "REASON=723"
Deploy the reason table. - Preference / Deploy Auxiliary - Select Reason codes, then GO - Select DSM or XAL for the store, then GO - Select Add or replace, then GO