How to implement Stripe Embedded Payment (In-App Payment UI) using Pega Constellation without redirecting to Stripe Checkout page?

Ok good tha you have manage to embed payment ui in your DX component. Showing vendor specyfic ui and then redirecting is standard thing. This is due to compliance and regulations - those screens needs to comply with law.

Coming back to your question, you migth need to redirect back to assignement not to a case. Take a look on this article: