Hierarchy View of Web Page presents is a tree structure view of the content in the currently selected ZUL Editor, it can be open by clicking [Window]/[Show View]/[Outline].
Each component in this tree structure has a special icon to distinguish different tag elements. Any modify on the zul file will update the tree content in Hierarchy View of Web Page immediately. You can also modify the file content by using mouse dragging node inside the Hierarchy View of Web Page or using right-click menu.