You can invite other people to join your logbook and share in your videos as well as add their videos to your logbook. In this way you can create unique private groups that can all record into the same logbook whilst still being able to keep their own private logbooks on their accounts as well.
To share a logbook, hover over the logbook title and time at the top of the screen:
You should see the share icon as the second icon with the 2 people. Click on it to get to the share screen.
On the share screen you will be able to add a new sharer via their emails. Enter one email per link and then click Send Share Invitations.
Existing sharers will be visible on the right.
NB. Sharing logbooks is a premium feature.