Hi Will,
Those fields are considered to be identity properties on par with the molecule name, which is also not editable in the document grid. The easiest way to get those values into Skyline is to import them as part of a transition list. Or, you could less formally add them in the document grid as a Molecule Note, e.g. "CAS=xxx HMdB=yyy". That's a new feature available in the current Skyline-Daily.
It is true that the molecule name can be changed with a right click in the targets tree, but we haven't provided for changing absolutely all possible properties there, and in any case that wouldn't be as scalable as desired.
Thanks for using the Skyline support board,
Brian Pratt