We have a sample for this use case here: https://github.com/azure-ad-b2c/samples/tree/master/policies/invite
Let us know what you think and if this fits your use case.
An error occurred while saving the commentFrank Lores-Penalver commented
May 2019, still nothing... This is a very important feature. Currently the only other options is custom policies, that as the documentation says clearly, should only be implemented by identity pros...