[itsme]

It is fine that "Keys" in the songs' meta tags is independent from the starting key for ChordPro transposing. That allows specifying multiple keys. 
But sorting them alfabetically has unwanted side effects. E.g. for "Dream A Little Dream" there is the wonderful Louis Armstrong version that modulates from G to Eb and is usually found in fakebooks. The also well-known version by The Mamas And The Papas modulates from G to E. When I specify both keys in the meta tags, MSP shows "E, G" which is not what I want to see. As a workaround I added additional entries "G - E", "G - Eb", "C - A" and "C - Ab" to the selection list for "Keys". That does the job for me but with many modulating songs in a library it would quickly create a confusingly long list of keys.
The new UI of the song editor would allow dragging the keys to the desired sequence.