Thank you for reaching out to the community forum!
I understand that you would like to add custom attributes to Entra users and provisioning attribute mapping from Google to Entra ID.
You can add custom attributes to Entra ID users by following the below article Create a custom attribute
https://learn.microsoft.com/en-us/entra/fundamentals/custom-security-attributes-add?tabs=ms-powershell
To map the Google attributes to the Microsoft Entra attributes please refer the below article.
Customize user provisioning attribute-mappings for SaaS applications in Microsoft Entra ID
Hope this helps. Do let us know if you any further queries.
Thanks,
Akhilesh.
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