Comment 10 for bug 1794588

In the XUL client, you cannot edit the call number of one item attached to a volume because of the structure of volume record and item records - Item records are attached to the volume/call number record and are subordinate to the vol record. The call number is directly associated with the volume record and not the item record. In order to change the call number of one or more items attached to the volume record, while maintaining the call number of other items on the same volume record, you must transfer the items to a volume record with the desired call number in the XUL client. If none is attached to the bib record, you create an empty volume with that call number and then transfer the item(s).

The same behavior is in the web client. The holdings display in the web client doesn't illustrate the structural nature of library to volume.call number record to item record as does the XUL client holdings maintenance display.