Thank you for posting your question on the community and I am sorry about the late reply to your inquiry!
Unfortunately, as mentioned in this knowledge article, Auth0 does not support any non-standard app-to-app linking flow similar to the one for Alexa. As the article mentioned, you can try the following:
Perhaps you might use the standard prompt=none as explained in Configure Silent Authentication and specify code as the response type. However, that implies that your app launches a browser (and that browser must have a valid SSO session so that the user does not have to authenticate again) and that will likely break the native experience of the App-to-App scenario.
Otherwise, there is an item in our backlog regarding being able to return an authorization code natively within the application without using a browser, however there is no ETA on this feature at this time. I would advise to submit a post on our Feedback page regarding this to bring more attention to it!
If you have any other questions, feel free to leave a reply!
Kind Regards,
Nik