Data adapter POST

Hi, how do we use POST in a composite data component? I have a data resource with a POST schema for request and response, but when I bind it to a composite component the fields available are only for the GET schema, which I have disabled. I also tried arbitrary, but no data is being sent in POST request / create record action. I want to create a signin/signup component.

Composite data components seem quite broken for this use case. And I don’t understand why. I am also trying to create a signing/signup component.