The only thing that I can think of is:
- Open Tag Browser to determine all the identifiers used
- Select one identifier at a time to limit affected books
- Highlight all
- Edit Metadata in Bulk
- Search and Replace Tab
- Search Mode: Regex
- Search Field: identifiers
- Search For: [expression, see below]
- Replace With: empty
- Verify test area results are correct
- Apply
I cannot think of the exact regex you would need. Roughly, it would probably be the identifier's name, a colon and then "all characters, greedy, until the next whitespace/word end". So something like...
ID:+.? Or is it
ID:.+? Hmm.. think I'm missing the word boundary. Anyway, I'm not sure if the expression is written correctly. But hopefully you've got the idea. I imagine that the colon might need to be escaped.
I would definitely suggest trying this on a sample database. Just to make sure that it doesn't harm anything else. Maybe create a new library and then copy various sample books into it, run the regex and see what happens.