Page History
...
After the component is dropped, the editor will remove the highlighting of the layout structure and will render the form as it would look like in a "real" client.
The "preview" setting, if switched if switched on, will keep the layout highlights all the time.
Layouts can be nested according to the following rules:
...
"div" can contain "component", "div"
The editor will change the cursor image to let the user know if a component or layout can or can not be dropped onto a layout container.
The screen cast below shows how to build a flow layout form using a predefined form layout structure.
https://drive.google.com/file/d/0B_hEnj_ZSycvMEw2VmktYzI3Qm8/view
Note: main forms should have a "container" as the root of the containment hierarchy, while forms designed to be shown in tabpannels should not have "container"s.