Thanks for posting your question in the Microsoft Q&A forum.
Azure only allows one redirect URL to act as the default in app registrations or authentication settings. The portal does not provide a direct Make Default button. Instead, the first redirect URL added is treated as the default.
To change it, you usually need to remove the current default URL and add the new one first, or update the redirect settings in your app’s configuration or code. This behavior is by design in Azure AD and App Service authentication.
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