Config files should be mature programming languages, not Yaml/Json files.
Might sound crazy but we built full web apps in just yaml.. Been doing this for about 5 years now and it helps us scale to build many web apps, fast, that are easy to maintain. We at Resonancy[1] have found many benefits in doing so. I should write more about this.
[1] - https://resonancy.io
This is essential to productivity for humans and LLMs alike. The more reliable your edit/test loop, the better your results will be. It doesn't matter if it's compiling code, validating yaml, or anything else.
To your broader question. People have been trying to crack the low-code nut for ages. I don't think it's solvable. Either you make something overly restrictive, or you are inventing a very bad programming language which is doomed to fail because professional coders will never use it.