The left navigation of the QSF (Quick Start Framework as we call it) is actually a stylized TreeView with added product icons to it. The examples solution which you browsing contains the examples themselves which aim to give you a kick start or reference when you are developing WPF applications.
If you are interested in building such a TreeView I highly recommend you to browse the code of the examples for the control.
There is a completely different solution for the QSF which available only to users who purchased developer license with subscription and priority support as a part of our Source Code offering. For more information please refer to our website.
the Telerik team