After a group has been added, you can click on the + next to the Display Group's name (shown right) to reveal the following options: Members
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The Members sub-section of a Display Group allows you to specify which Recipients and Groups are a member of the selected group.
To add a member to the member list of this group, simply click on the name of the Recipient or Group under the "Non-members" category.
To remove a member from the member list of this group, simply click on the name of the member under the "Members" category.
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