When I manage a project and have the freedom to choose my configuration structure, then I always use typescript. I never understood the desire to have configuration be in ini/json/jsonnet/yaml. A strongly typed configuration with code completion seems so much more robust. Except of course your usecase is to load or change the config via an API.
You can apply typescript-based strong typing and code completion to JSON and similar. And then you can avoid making arbitrary code execution part of your config format.
I like what apple is doing with https://pkl-lang.org/ though.