Updating recurring gift: card, schedule via API

We would like to provide our constituents with a custom interface for managing their recurring gifts. We think we'll be able to list out recurring gifts via the GET Gift List endpoint, and we think we could even terminate or cancel a recurring gift via the PATCH Gift endpoint.

But we don't see any API documentation for updating the card associated with a recurring gift or for how you might modify the gift schedule for a recurring gift. Is that possible?

Or would the preferred method be to cancel an existing recurring gift and initiate a new one?

Thanks for the guidance.