[jecilop]

UPDATE: Solved as of post #2
ORIGINAL POST:
I am talking about batch searching all files (epubs) at the same time. This isn't something in the Edit Metadata fields.

During some tag management modifications, I added a tag to all files in a new tag column and deleted it from the original column. It wasn't supposed to be added to all files.
Now that it's gone from the original column, I can't identify the books it belongs to (I track my source for the book this way).

HOWEVER, I haven't Polished the metadata in the files yet including the metadata jacket so that tag name which is unique is still contained in the files.
If I can pull a list easily of files containing this, then I can quickly fix it.