We acknowledge the customer demand for Private Channels and have been hard at work on it. Private Channels is currently in preview with a select group of customers. We expect to release the feature to the public later this Fall, and will update here when we are starting to roll out to all customers. We appreciate all the feedback you have provided to us on this forum and thank you for your patience.
~AlexMike Bakke commented
Hi - good news development is active. If there is a priority for the 5 types, I'd say #5 (secret) is the most immediately useful (for me)
This feature item is still in the works. We will keep you posted as we have new info from the feature team.
Thanks to everyone who volunteered for testing the Office 365 group calendar. The TAP team will be reaching out as we are closer to being ready.