It would be very fine if one could assign variables from command-line.
Example usage scenario (real life): I have two identical external HDDs, "Backup 01" and "Backup 02". They are labeled accordingly. I have two projects (Backup 01 and Backup 02), which contain sync sessions for these drives. Drive contents is identical - I just want two copies of data. Trouble is, I can't assign two drives (even if they are not attaches simultaneously) one letter in Windows - that's why I can't use predefined drive letters in sessions. And I can't use drive name variables, because drives are named differently.
Most comfortable scenario would be passing just-attached drive letter to wndsync.exe in command-line (I can do that from autorun-handler), and then use in session as variable.