I heard a rumor that a new program was(is) being designed.....
Yes you can add new codes but it all depends on your password level.
I believe CIVAB was publicly funded as it was also available in book form,free of charge to public hospitals but from 2009(last printed version) the funds were no longer available.
It could be that the CIVAB codes are kept upto date for Si3C users,I'll do some digging.