To use the pop-up menu in the command view, position your mouse pointer
  in the message region, and press MB3.  The debugger automatically
  inserts your last command in the [last command] menu item of this
  pop-up menu.

  Menu items are as follows:

  Repeat Command         Re-enters your last command.
    [last command]

  Clear Command Window   Clears the command view and displays
                         the DBG> prompt.

  Clear Command Line     Clears command line.

  Step                   Step to next line, stepping over routine calls.

  Go                     Resume execution of program.