Further to my suggestion, it would be useful if the Output bar could be used to display the extracted text. Even better, would be if this could be updated in realtime, similar to the incremental search, so you can see immediately the extracted text as the Find/Replacement expression is modified.
This would make it far easier to create the correct Find/Replacement expressions, since it would give immediate feedback on what is matched (ie. the current incremental search feature), along with what is extracted.
While this real-time updating is probably not feasible for Find/Replace in Files with the option “Look in Subfolders” enabled, it could come in handy when the “Look in Subfolders” is not enabled.