Syntax:  SET BUFFER OVERVIEW boolean

  Enables or disables overview operations in the current buffer.

  This command enables or disables the source elision commands and the
  EXPAND command on an overview line.  By default, overview operations
  are allowed in a buffer when it is created.  The parameter value off
  disables overview operations.

  RELATED COMMANDS:

     COLLAPSE                    SHOW BUFFER
     EXPAND                      VIEW SOURCE
     FOCUS