From the Graphical Editor window open the Edit menu
and select Add Global Self-Loop or from the toolbar click on the Add Global Self-Loop
button .
This will open the Self-Loop Transition Editor dialog box.
By default, the window only shows events that have not been used. This can be changed by unchecking the Only show unused events checkbox. Select the event you wish to use from the list and click OK. The global self-loop will be added to the Global Self-Loops pane. This will create a self-loop for every state of the DES using the selected event.
Please Note: Global self-loops are not displayed graphically in order to save space and clutter in the DES editor workspace.