VMS Help EDIT, /FDL, Parameter  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 fdl-file-name

    Use this parameter to specify the FDL file to be created,
    modified, or optimized during this session. If you specify an
    existing FDL file for modification or for optimization, the
    output file is the next higher version of the file being modified
    or optimized. In all cases, you have the option of using the
    /OUTPUT qualifier to specify the output FDL file. The default
    file type is .FDL.