Hi , To answer this please check below
Configure the app manifest
To configure the application manifest:
- Sign in to the Microsoft Entra admin center as at least an Application Developer.
- Browse to Identity > Applications > App registrations.
- Select the app you want to configure.
- From the app's Overview page, select the Manifest section. A web-based manifest editor opens, allowing you to edit the manifest. Optionally, you can select Download to edit the manifest locally, and then use Upload to reapply it to your application.
Please find this doc for detailed explanation
https://learn.microsoft.com/en-us/entra/identity-platform/reference-app-manifest
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