Delete Missioon Codes???

I am developing a session using Pguy tools including Enhanced Towers and Mission Codes. I find that once I create a mission code I am unable to delete or rename that particular code. If you delete a particular code it appears to be gone until you reopen the session pull down and click on Mission Code Manager. I've tried deleting the Mission Code Manager Rule and reloading it, but the unwanted mission codes are still there??? Everything else, including defined paths and mission codes work fine. Any suggestions? I am running TRS 19 on a Mac.