Actually, there is no reason macro-based metaprogramming couldn't work in a language that uses graphs as a priimitive UI element, rather than a list like LISP does. "Graph rewriting" is practically a cottage industry.

Where you wrote "UI element", did you mean "data structure"? I don't know what it would mean to talk about graphs as a primitive user interface element.

With a language with sufficiently expressive metaprogramming facilities (LISP enthusiasts will recommend LISP for this role) you can extend it with whatever data structures you want.