Some BPMN elements can not be represented on any BPMN diagram. You can use these elements as data types for specifying values of other element properties. This kind of elements can be created in the Containment tree.
To create a BPMN element in the Containment tree
Right-click a package in the Containment tree.
From the shortcut menu, select New Element > BPMN Element, and choose a BPMN element that you want to create.
To open an element Specification window, do one of the following
Right-click a selected symbol and from shortcut menu, select Specification.
Double-click a symbol on the Diagram pane or in the Model Browser.
Select a symbol on the Diagram pane and press Enter.
Add a model element to an owning model element in its Specification window. The second Specification window opens on top of the first. Use the Back to or Forwardto arrow buttons for switching between windows.