The Insert Element... menu item allows you to place one
  or more elements or groups into one or more groups.

  If you specify a group name in the Element field, CMS
  inserts the elements contained in the group.  For example,
  if you insert group A into group B, group B will contain
  the elements in group A.

  If the contents of group A change at a later time, the
  contents of group B are not affected.

  To insert a group into another group, choose the Insert
  Group... menu item.