Syntax:  SHOW PLACEHOLDER placeholder_name_wild defined_language

  Displays the definitions and characteristics of one or more
  placeholders.

  If you specify a placeholder name, LSE displays all the attributes
  associated with that placeholder.  If you specify a wildcard
  placeholder name, LSE displays brief information about each matching
  placeholder.

  You can navigate through the list using Ctrl/F (forward) and Ctrl/B
  (reverse).  Ctrl/E (expand) lets you display full information about
  the indicated placeholder.  The COLLAPSE command reverts back to the
  brief display.