Thank you for posting this in Microsoft Q&A.
As of ow we do not have an option to create groups in Azure AD B2C.
However, when you create Azure AD B2C tenant, there is Azure Active directory also that gets added in the tenant.
But both are different. You can create multiple groups in Azure Actie directory within B2C tenant. And once you access users in B2C, you can make users member of any group which is created in Azure Active Directory.
You can access users blade in B2C tenant and you will have to go to each users and make them member of any groups that you want to keep them in.
However, using those groups in any of the policies is not supported yet.
Let me know if you have any further questions.
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