Library /sys$common/syshlp/dbg$help.hlb DEBUG, Built in Symbols, %NEXTOUTPUT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Specifies the next output display after the current output
    display in the screen-mode display list. An output display
    receives debugger output that is not already directed to another
    display.

    Example:

    DBG> EXTRACT %NEXTOUTPUT OUT4.TXT