Hello, KK 2014.
The QML Sample App is a hybrid app. The code managing the list of samples and presenting the content (sample descriptions and source code list) is written in a combination of C++ and QML.
We plan to move all the code for the sample to Github in an upcoming release. When it is there, you will have access to the source and have the opportunity to contribute to the sample application itself.
Qt offers a wide selection of samples for developing UI elements. You can see these in Qt Creator by selecting Welcome (the top item) on the Mode Selector. You can refine the list by searching for "QML" or "quick". Looking through these may inspire you to create an even better UX.