In my organization's use of Retain we've found several times when having the ability to exclude a phrase in the search would have been very beneficial. We've tried putting a quoted phrase in the not contains field but it appears to treat it only as a string of words and not a phrase. When we contacted support about it we were told that the UI did not support that. Curious, I consulted with a developer that uses Solr extensively and was told that the actual underlying engine should be able to support it, so it appears to just be a UI limitation. If possible adding that feature to the search would help us in servicing records requests in the future.