The Management of IPTC fields it's not possible through applications of Sinar.
The IPTC fields are fully editable through applications such as Adobe* Bridge / Lightroom, Photo Mechanic etc.
Enable the metadata tab, select an image or many images (batch), modification of the field "Creator", that's it, easy and fast.
*Changes of IPTC metadata in DNG files, recorded inside the file only through Adobe's applications. Third-party applications, create additional XMP metadata file (side car file). That, maybe to complicates the management of collections.