With Bug 12747 we added the AdditionalFieldsInZ3950ResultSearch. This currently works in the z39.50 search for the basic editor and in the z39.50 search in acquisitions, but does not work when starting the z39.50 search in the advanced editor for cataloging.
*** Bug 23907 has been marked as a duplicate of this bug. ***
This would still be very useful. Some libraries have a particular field that they use as a quick quality check and it would be good to have the info in the results rather than needing to open the marc view to compare records before importing.