This is not yet supported. The best way to organize sets so that they are picked up by OrangeCD is this - create two subfolders CD1, CD2 etc and place mp3 files into corresponding subfolders. You can leave images, notes, etc. in parent folder - it will be scanned in addition to CD1, CD2.

Your way of organizing multi-disc sets will be supported in future but I don't have ETA date.

Andrei