Thank you for posting this in Microsoft Q&A.
As per our public documentation of Azure AD, there is no role by name "Organizational Branding Administrator".
https://learn.microsoft.com/en-us/entra/identity/role-based-access-control/permissions-reference
To configure your company branding you will need to have "Global administrator" role assigned to user account.
https://learn.microsoft.com/en-us/entra/fundamentals/how-to-customize-branding#prerequisites
Specific permission required to configure branding is, "microsoft.directory/loginOrganizationBranding/allProperties/allTasks"
Currently this permission is not listed to get it added in custom role creation. This is user base role and currently we only have below permission that can be defined for user in custom role,
You can submit feedback in Azure feedback portal to get this permission added in custom permissions.
https://feedback.azure.com/d365community/forum/22920db1-ad25-ec11-b6e6-000d3a4f0789
Let us know if you have any further questions.
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