Library /sys$common/syshlp/lse$menu.hlb SET_PLACEHOLDER_DUPLICATION  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Syntax:  SET PLACEHOLDER DUPLICATION duplication defined_placeholder
              defined_language

  Specifies whether a list placeholder is duplicated horizontally or
  vertically.

  A list placeholder is duplicated when you type over it.  This command
  specifies whether the duplicated placeholder appears on the same line
  as the current one, the next line, or either depending on context.