https://forums.cncnz.com/topic/15696-is-there-a-way-to-enable-all-units-in-campaign-and-co-missions/?tab=comments#comment-196256
Not sure why this code has to be entered in such an obscure way, instead of just making it an option in the configuration menu. Also, not sure why this wasn't done decades ago, as it gives the campaign a whole lot more replayability.