An error occurred while saving the commentD. S. Taylor commented
Here's an answer: First click your first individual in the group, then add the additional members via the Add People button. You'll create a group. Send an initial chat. Then, where the names are listed at the top, click the Pencil icon to rename the group. This gives you the group chat function and many other feature of a regular Team (like Files). Finding it again is still a mystery to me for now.