The Member Of tab allows you to add the user to the User Group, where the user is created can be a member.
Note: You can also add the User to a User Group through the Group Tasks. You can learn more about that in this article.
To add the User to a User Group, click the Add button from the bottom of the groups' list.
This will open the User Editor-Groups window, from which you can select the Group to assign the User.
Once you select the Group, or if necessary, click Select All, then click OK to save the User Group for the User you are creating/modifying.
As soon as you Save it, it should be visible on the Group List.
To delete the user from an assigned User Group, click on the User Group name from the list and then the Remove button under the list:
A new window will pop up, asking you to confirm the deletion.
Once confirmed, the User Group will be deleted from the list, and the User will no longer belong to that User Group.
Watch the video below about the Member Of tab when Adding a New User.