Each Separator control will create a visual border wrapping all other fields underneath it. This group is terminated if a control of type Heading, Separator, Heading with checkbox, or Heading (Collapsible) is encountered.
In this example, six textboxes are separated by a separator control. As you can see, there is no graphical element for the separator itself. Rather, the outer frame that would have surrounded all six textboxes, are now separated into two frames surrounding the elements before and after the separator control.