If you are making your own formats of YAML files, you may like the article that we wrote showing how to make Visual Studio Code and a few other text editors to recognize a YAML file schema and support code competition.
The magic is about defining a JSON schema that is hosted in a public location. JSON schemas work also for YAML files.

Check out the article here: defining data contracts in Visual Studio Code with code completion

You can also find the full source code, because the platform is open-source: https://github.com/dqops/dqo

If you can confirm that it also works for you in your favorite code editors, that would help me progress with this feature.