[bhrgunatha]

It's actually used in Dr Racket. Although to be honest, I don't find that I use it very often. It's still a nice feature to have - for example to see where arguments are used inside a scope block and where values leak into scope e.g. when mis-typing a name.

[gus_massa]

Arrows are also useful while studding unknown code. For example, if the code is

  (do-something (create-something  height width7))

I use the arrows to connect the appearances of the unknown functions do-something and create-something with their definition and then read the definitions, and perhaps add more arrows there to previously defined functions. I usually remove the arrows when I understand that the function is not related to my problem or when I understand what the function does.