There are some hidden/transparent commands that override command aliases. For instance, I tried to use "SS" as subtract and "U" as UCS but both "SS" and "U" already have built in commands that are not customizable. I like to keep my left hand on the keyboard and my right hand on the mouse so that I can be an efficient drafter, however these transparent commands keep me from being the most efficient. Customization of these transparent commands would be very helpful because then aliases would be fully customizable with no limits.