/sys$common/syshlp/helplib.hlb SET, DISPLAY, Parameters  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 display-device

    Specifies a logical name for the workstation display you are
    creating or modifying. If you are directing application output
    to multiple workstation displays, you can use different logical
    names to point to each display. If you do not specify a display-
    device parameter, the logical name DECW$DISPLAY is used. This
    means that, by default, application output will be displayed on
    the workstation display device referred to by DECW$DISPLAY.

    By entering the command SHOW DISPLAY, you can see the default
    workstation node where applications will be displayed, as well as
    related device, screen, and transport information.

    If you specified your own logical name in the SET DISPLAY/CREATE
    command, include that logical name in the SHOW DISPLAY command.