Library /sys$common/syshlp/dtehelp.hlb SET, DTE, /ESCAPE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /ESCAPE=character

    Selects the escape character. The escape character is used to
    quit DTEPAD by pressing Ctrl/escape-character.

    You can select the escape character from any ASCII character
    between @ and z, except C, M, Q, S, Y or the left bracket ([).
    You cannot select a character currently defined as either the
    break character (see the /BREAK Subtopic) or the command
    character (see the /COMMAND Subtopic).

    By default, the escape character is a backslash (\).