[sciurius]

ChordPro is designed for making professional songbooks and tries to prevent unexpected surprises by limiting what it accepts as chords.
A chord can be

• known (built-in or defined, with diagram) or
  
• well-formed (a known root note follwed by a known qualifier and extension).
  

For special cases, you can select in the config:

• a relaxed mode (known root note followed by arbitrary) and
  
• a note mode where lowercase root notes are accepted (and transposable).
  

For MSPro this would be overkill, I think. An easier approach can be to split the chord into parts is it contains a slash, and transpose each of the parts if it looks transposable, regardless of case.