Thank you for posting this in Microsoft Q&A.
I understand you want to add custom attributes to your enterprise application.
To assign or remove custom security attributes for an application in your Microsoft Entra tenant, you need Attribute Assignment Administrator.
Please follow the steps mentioned in this documentation: Manage custom security attributes for an application
If the above is not your scenario, please correct me and provide us with detailed step.
Hope this helps. Do let us know if you any further queries.
Thanks,
Navya.
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