I agree with Deadeye, Its practically the same thing. I think it may even end up destroying readability for those really long expressions; you'd have a pyramid sky high.
I just can't think of anything that doesn't involve a picture of five apples over a picture of three apples and a cartoon worm wearing glasses asking how many apples there are all together.
Basically, exactly the same way it is now, but with more information on what that particular step does.
I think that's what the wiki is for though, all the expressions are explained clearly. It could use some expansion however.
It would be great to find a middle ground like Davo said; between text and graphics. I just don't see how multiplying by 3 with (*3) in text is any more complicated or unreadable than a square or node which says multiply::::__3___::::: __number__:::::.