You are right about this, it is exactly what is hard to do! it is possible to do some form of this, where you have well behaved "macros" that create diagrams of

You are right about this, it is exactly what is hard to do! it is possible to do some form of this, where you have well behaved "macros" that create diagrams of particular shape "at runtime" (forall n. the diagram with n copies of n)