Library /sys$common/syshlp/dbg$help.hlb DEBUG, Command Summary, Editing Source Code  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    The following commands are used to control source editing from a
    debugging session:

    EDIT                   Starts an editor during a debugging
                           session
    (SET,SHOW) EDITOR      (Establishes, identifies) the editor
                           started by the EDIT command