I notice or at least could not find, that the IPTC description is missing from the Synchronize Metadata dialog. The Headline is there but just below it is IPTC subject code. Can this be added?
Use the Basic Info: Caption field in the Sync Metadata dialog.
In accordance with the industry standard, the LR Caption field (shown in the Default preset of the Metadata panel) is linked to file metadata fields IPTC:Description, EXIF:ImageDescription, and XMP:Description. So if you enter a value in the Caption field in the Metadata panel, it will also show up in the IPTC Description field and vice versa. And that value will show up in the three previously mentioned metadata fields stored in the file.