To add a character, simply type it; it will be added to the left of the
current position.
This also includes the newline character; to start a new line, press
carriage return.
  will prompt for the name of the def in the command window with
 I
>; type the name of the def and press RETURN
 .
will insert an instance of the def to the left of the current position and move the tree cursor to the first parameter.