if you are talking about creating a game with a custom starting positoinis see here:
https://www.chess.com/clubs/forum/view/4pc-variant-custom-starting-position
this has nothing to do with PGN however (PGN4 are moves 1. h2-h4 .. etc) and FEN4 is a position.
not sure what your question is..
How do you publish a game after it has been edited in the pgn editor? (4 PLAYER CHESS)