As said before, Gaphor is highly visual oriented. The content of a model should be displayed in the diagrams, and only there. When double-clicking on a diagram in the tree view, it is opened in the diagram view. Items can be created with the tools and existing items can be dragged from the tree view.
All actions that can be done on a diagram item can be reached by a popup menu under the right mouse button. This way attributes can be added to classes and extra segments can be added to lines.