Editing a model consist of a combination of the following actions:
All editing actions can be undone (CTRL+Z) and redone (CTRL+Y).
To create a new model element, use the contextual menu item New > Object.... You are then expected to select in a dialog the type of instance to create.
The New contextual menu shows the most recently used types, to avoid having to select those types in the dialog each time you want to create an instance. The contextual menu reflects the current selection in the model editor:
If a model element is selected: the dialog allows to create a new instance and to select a reference to connect this instance to the currently selected model element. You have the opportunity to browse by reference or by type:
You can modify the attributes of a model element using the Properties view.
To add a reference from the model element selected in the editor to another element, use the contextual menu item Add > Existing Object....
The Add Existing Objects dialog provides buttons to add, remove and reorder elements connected to the model element selected in the model editor.
You can also add and remove references of a model element using the Properties view.
You can delete a model element using the Delete contextual menu. A Delete dialog enables to control the delete command: