I may be using the wrong control, and if so please point me to the right direction.  I am trying to use a collection of  ThemedContainers to behave as a button along the left margin that will be originally all collapsed and individually expand when clicked.  I cannot seem to find how to set the collapsed property at design time or programmatically control these at run time.  Please point me to the right events or properties...

You can certainly use the ThemedContainers for that purpose (when you put them in a FlowLayoutPanel that will control the formatting when they are collapsed), but if you have several of them, you may want to consider using one of the navigation tools from DevExpress or Infragistics.  However, when you do that, you will lose some of your functionality, because each individual panel on those is not a control and therefore, you cannot add the same types of children to them as you would with the ThemedContainers.

As for the collapsed state, try the InitialBodyVisibility property for the initial state and the IsBodyVisible property for changing it at runtime.