the best language by a mile for dsl-as-data-structure is kdl2

it reads like code and you can easily define a schema too

well that's what i am using

https://kdl.dev/

and https://crates.io/crates/knus/ to define the schema

actually more than that. it would be awesome to have a programming language whose code is also valid as kdl 2. like lisp code being composed of s-expressions