Just for the record, after some hours of frustrating guess-work, the filter ID AKA 'filter hint' of the 'new' RTF export filter was revealed to me. It's actually almost documented in the maker.ini file, but I suspect that I'm not the only who couldn't read between the lines.
'0001ADBIRTF ' There you are. ADBI is Adobe India. The hints from maker.ini: --- [APIClients] ;ClientName=ClientType, [facet, format_id, vendor_id, display_name, ] ; description, path, mode, optional file extension for filter ; when ClientType is filter type, facet, format_id, vendor_id and ; display_name are required. ; mode can be one of maker, structured, all. it determines for which ; mode(s) to load this client. ; for example, RTF=TextImport, RTF, RTF, FAPI, RTF, Rich Text Format ; (RTF) Import, filters\rtfimprt.dll,all,^.rtf Microsoft RTF1.6=ExportFilter, RTF, RTF, ADBI, Microsoft RTF1.6, RTF Export, filters\ExportUtility.dll, all, ^.rtf --- The syntax of a filter hint is described in general on page 663, and the FS_SaveFileTypeHint is described on page 154 of the FDK Programmer's Reference (for FrameMaker7.0). A filter hint consists of 6 fields (without spaces between them): record_vers vendor format_id platform filter_vers filter_name The first 3 fields are each 4 bytes, space-padded if shorter than 4 bytes; this 12-byte string is what's needed for F_ApiSave() and corresponding commands in e.g. FrameScript. The only part missing from maker.ini is the 'record_vers', which is apparently always '0001'. Kind regards Peter Ring