This is how I did it per your instructions:
Created Custom column with {identifiers:select(amazon)} so now I can see the books with amazon numbering in a column next to ISBN column
Created this template in saving to disk preferences {identifiers:select(amazon)} - {authors} - {title}
This did it books are saved with (amazon - author - title) filename.
I wonder, could I use two identifiers at the same time (something like if one is empty use the other)?
This program never misses to amaze me.
I love Calibre, it has saved me hours in book archival.