[ahopebailie]

The APIs aren't really designed to solve for this.

If the site knows you and has payment credentials stored they won't need to use Payment Request API (although they still can).

Storing payment credentials differs by payment method. If you're talking about card payments then you have to deal with things like PCI-DSS and/or tokenization but there are other ways to pay which may support this use case more explicitly, for example by capturing explicit permission from the user to allow the merchant to make future purchases seamlessly.

This is something we're trying to find a standard protocol for with https://openpayments.dev so that the ecosystem is less fragmented. But, this is not linked to the W3C work explicitly