There are several plottingPanel in the following example
1. You need to add a new "Panel" (replace the current plottingPanel) and set the Layout from default border to Grid
2. Move the current plottingPanel under "Panel" (as a child of Panel)
3. Add more PlottingPanel under Panel
4. Move trace under each PlottingPanel (Right mouse click, select [b]reparent[/b], then enter name of the parent element)

The following is a swf movie. It shows how it can be done. (You need to set up more properties)