Design items such as requirements, use cases, risks, specification, test cases and test runs are stored in a tree structure on left side of the screen. If you select an item, the url in the browser will change and the item will displayed on the right side. You can also just type change URL in the browser and hit return to load an item. The browser's back and forward buttons work as well to quickly switch between items You can open several items at the same time in different tabs, to quickly compare them. 
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