UML Navigator

The UML Navigator is one of the views that makes up the UML Perspective, which you can open through:

Perspective > Other > UML Or you can open it as a view in any Perspective:

Perspective > Show View > Other > Together > UML Navigator

This tree view shows the hierarchical order of the diagrams and diagram elements in the project.

The top level of the tree represents each project that is currently open. Through this view you can navigate through the project, opening diagrams and adding additional elements.