Tools->ExportFilter->ExportEPD (Sorry, but it's only in SVN at the moment)
HGM - i gave an old xboard a test and (like SCID vs PC), it does not honour the EPD hmvc and fmvn valuesThis feature runs through the filter, and exports select games to a basic EPD file. Only games with non-standard start positions, or those that load into ply (for example, after a material search, or after Search->Filter to last move), will be saved. Note - subsequent loading of this file may show fewer positions than (non-standard) games, as EPD files discard duplicate positions.
to set the FEN accordingly when the line is loaded. It's not going to make much diff supporting this though i guess.
https://www.chessprogramming.org/Extend ... escription
Cheers, SteveOne EPD string or record consists of one text line of variable length composed of four fields separated by a space character followed by zero or more operations. The four data fields, which describe the position, are common with the FEN-Specification, while the halfmove clock and full move counter, obligatory in Forsyth-Edwards Notation are replaced by optional hmvc and fmvn operations, and 0, 1 are their default values