The delete metadata erases also the current record that I would like to keep (the one that I see on the pane). I need to keep the info from the caption for each file since only the photographer knows what describes the content of the photo. PM reads out and shows the correct IPTC/XMP data (except when some older Fotostation versions have been used for the initial IPTC writing).
Thus the requested feature should leave the current record untouched and just delete all previous IPTC records, so that I get a clean file according IPTC/XMP standard, that can be interpreted by all applications that follow these standards.
Most users might have not encountered problems with previous IPTC records, since they are not visible in PM. I was not aware of it too until I was shown screenshots of the IPTC/XMP readout of other applications, such as image bank databases and in some cases Adobe InDesign.
I have performed extensive tests with all sorts of applications regarding IPTC/XMP handling and came to the conclusion that PM is the only tool that handles IPTC/XMP correctly according standard. Not even the Adobe products keep a stringent interpretation of IPTC/XMP. And depending on the software that was used to write the IPTC record initially you get different results in the end even if PM was used as a second IPTC writer when updating the file.
Maybe it might even help to set PM by default to delete all existing (invisible) previous IPTC records and just keep the last one and update this to IPTC/XMP standard.