The GraphQL API runs on port 8911. Have you tried the GraphQL Playground for your App?
http://localhost:8911/graphql/
This is coming from api/src/functions/graphql.js
If you were to create a new function, say api/src/functions/test.js, you could inspect it at http://localhost:8911/test/
Here’s a comment with an example.
Lastly, on the front-end you may find React Developer Tools browser extension very helpful.
Is this what you were looking for?