Thank you for posting this in Microsoft Q&A.
I understand you are trying to add new claims to your application, but the option is greyed out.
This is because there are claims defined using claim mapping policy through Graph or PowerShell. You need to remove any claim mapping policy from your applications to define new claims and attributes here.
You can check any existing claim mapping policy defined in your application using PowerShell commands.
Azure PowerShellCopy
Connect-AzureAD
You can remove claim mapping policy using
Azure PowerShellCopy
Remove-AzureADServicePrincipalPolicy -Id
Once the claim mapping policy has been removed from the application, you will get an option to add new claims.
Let me know if you have any further questions.
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