There is a sample model on the ParallelAgile.net website. It's an exported xmi file, but you should be able to import it into an empty EA model.

Another possibility is to define "extension points", e.g. so you could define your own Express.js "middleware functions" from a different folder, so they're not overwritten by subsequent code generations.

Swagger docs are automatically done, and they connect to the auto-hosted API for immediate testing. "Try it now" button in Swagger is active.
CodeBot also generates JSON Schema documents from the domain model, so these can be used to validate incoming data to the API. They can of course also be used elsewhere in your project if needed.