Note that if you demote a member in the community, such as from manager to member, he/she will still retain his/her highest set of permissions. For example: If someone in the Moderator role is demoted to a group member, he/she still retains the permissions assigned to moderators.
To edit a community member's type of membership:
In the Group - Membership List widget, click More beneath the usernames. The list of users appears.
In the Membership Type drop-down list to the right of the username, select the new membership type (owner, manager, member).