Connectors is an application for making structured/connected drawings in Morphic. It adds a new kind of Morph (NCConnectorMorph) that can connect other Morphs together (and stay connected). There are also a number of other shapes, flaps, and tools for making your own drawings.
It comes with some sample shapes in flaps for making UML class diagram and state diagrams.
It's also a framework for making your own structured drawing editors. There is an easy to use API for querying drawing structure, constructing drawings, and more.