The boxes seem to be an unstable medium between the stable points of S-expressions and indentation as nesting. If there are lots of nested expressions, you eith

The boxes seem to be an unstable medium between the stable points of S-expressions and indentation as nesting. If there are lots of nested expressions, you either push them to multiple lines and it becomes indentation, or you keep them on one line and the top and bottom boundaries of the boxes run together until you effectively have parentheses. Have you looked at Chuck Moore's ColorForth, though? It might be a neat direction to take this in.