Hi,
I've figured out how to do what I want. Had created a custom field the other day called ASIN that's based off the amazon: field in Ids {identifiers:select(amazon)}
Then I used search
Code:
#asin:false and isbn:true
on the main window to select just the books that have an isbn but no ASIN. For my purposes any number will work as the ASIN in order to sync Kindle's furthest read page so I can read the same book on multiple devices without losing my place. Some of my books have an ASIN populated by another process see
this thread.
Then I selected all the books in this list and used Edit Metadata in bulk with Search and replace and a regular expression. Either of these seem to give me the desired result.
After posting the original note I looked closer at a number of individual threads here for ideas and realized there was a way to properly qualify the rows I wanted to change before using the search/replace in metadata.
I love Calibre more than ever!
Rob