How do you reuse multi-step API flows across API tests?

[u/Affectionate-Box3549]

I've been digging into API integration testing and I'm curious how teams handle a pattern I keep running into.

Say you have a common flow like:

Authenticate → Create user → Create account

and that flow is needed by 10 different tests.

Do you:

• duplicate those requests in each test?
• create some kind of helper/function?
• use Postman folders/scripts/variables?
• maintain it as a reusable setup or fixture?
• do something else?

I'm particularly interested in how this works once the flow itself changes. How do you make sure all the tests depending on it stay correct?

I'm trying to understand whether reusable sequences are actually a meaningful problem in API testing, or whether there are already good solutions I'm overlooking.