A Group Manager is someone members can see as the manager of their group. Onboarding emails come automatically from the primary Group Manager, which is based on who was added first into the community.
All Group Managers appear to members in the Lounge. To see the managers (if the setting is visible), go to the Member Directory by clicking Members in the Feed, choose Members in the upper left, then choose Managers from the dropdown list.
To learn more about different manager account types, click here.
Here's how to add or change the Group Manager.
While in the group, choose Settings, click on Managers, click + Add new manager link, type the member name or email in the popup box, choose the member, and then click the Save button.
Group Managers do not have the full capabilities of a Community Manager. Also remember that even if a Community Manager isn't listed in the group as a Manager, they still have full admin access to the group.
Here are instructions on adding a Community Manager or Account Owner (access to billing and custom domain).