I am aware that in a mock server feature file, it is possible to forward requests to a specific endpoint using karate.proceed(): https://karatelabs.github.io/karate/karate-netty/#karateproceed.
We recently decided to opt for Javascript mocks, as they enable us to write more complex business logic for simulating the API we consume. Is there out-of-the-box functionality equivalent to karate.proceed() that I can use in a JS mock? Is there a way I can invoke karate.proceed() within this mock? Or is one expected to write Javascript code to enable this functionality?

API Mocking - How do I implement request forward while using a Javascript mock?
Great question, and yes there is no context.proceed(). You need to use context.http() and manually create a new request and handle the response. All the data you need will be on the request object. For example request.method will give you the HTTP method as a string.
This is indeed an un-documented part of Karate, yet to become "mainstream". Feel free to add a feature request for a context.proceed() that will auto-use the request in scope, that does sound useful. If you could contribute a PR or two that would be awesome :)
