I see. I was hoping for some way to use the alias of an input source to derive the output name from.
The Copy and Paste (the paste part) does not work on Mac. Instead, it just bings.
Aha, Batch Processing offers exactly what I was looking for, thanks for the hint. I was not looking in that direction. It is an rather easy change of configuration. As I am processing one file per month with this transform, I was not thinking of batch-processing 
Thanks, best
Jochen