Heartbeat organizes conversations into channels to bring organization and clarity to your community. If a channel becomes better suited for a closed audience, it can be converted to private.
How to create a private channel:
When creating a new channel for a group, first turn off the Set as Default Channel button
Then toggle on Set as Private Channel button
Select the groups, members, or roles you want to be able to access the channel
Now, this channel will not be discoverable in All Channels.