Postman - Collections, How to export testing credentials to a json, so I can later use it as a starting point to another collection?

Question

So my problem is, that we are depended on 3rd companies that doesn't have way how to automatizally via postman skip some steps. This testing is on testing enviroments on purpose, so no mocking there.

Flow is:

1. I need to make users, do partiall onboarding
2. I need to send list of those users to that company and ask them for approving them (in testing)
3. Finish the onboarding and rest of the E2E tests

Now it's done that 1) dumps me in the console those details (I make that json manually after that), so I am looking for a way how to generate json right after 1) collection ends so I can use it as an entry data for 3) collection.

Newman is fine, really anything that you will come up with will be. I am just kind of lost there. Is it even possible?

Thank you!

I tried to find answer in postman doc, searching thru web. Looking for videos, similar issues. No luck there.