[NTG-context] PDF custom properties

I should like to set the PDf properties so that the Document Info panel has Editor ... Title ... Subtitle ... Subject ... Keyword .... The problem is that currently \setupinteraction[subtitle=text,] goes to Subject and that there are no keys to get output labelled Subject or Editor. I have experimented with \pdfbackendsetinfo{ key }{ Text } but, so far, unsuccessfully. If this is possible,any suggestions about how to do it will be most welcome. Alan