Syntax:  DELETE MARK mark_name

  Deletes the indicated marker.

  If you do not specify a name for the marker, LSE deletes all markers
  at the current cursor position.

  The marker name can be abbreviated or wildcarded, but it must be
  unambiguous (that is, you can only match one marker.)

  This example deletes the marker named 1 from the list of markers in
  your current buffer:

                LSE>  DELETE MARK 1