The Storyboarder Tab is where most of the work on your scenario will happen. In the Storyboarder, You will see the flow of your scenario, and can add, edit and delete Nodes. Here is where you link nodes together to create the scenario. By default, the storyboarder contains a Begin Node and a Setup Node.
The context menu is opened by right clicking on an empty area in the Storyboarder. From this menu, you can choose to create most of the nodes used in Modest3D, ranging from loop nodes to setup nodes.