Here's one way of using it that is quite useful to me : make a separate model and diagram folder. I put all the UML components e.g: Class, under model and make all diagrams under diagram folder. With this I could reuse the same classes definition on several different diagrams. Any change to the class will be reflected automatically to others.
It's a bit more work since you have to do things in several steps :
- add any model under folder model e.g: right click on the folder -> Create Model -> Add Class
- Open the diagram and drag the Class there from structure view
It's not always seems practical to do so though, for quick "drawing" I just use the toolbar and let everything e.g: classes and diagrams on the same folder. However, for relatively serious UML Diagramming separating models and diagrams is more convenient.