...
Custom commands can be assigned to one of the five custom toolbar buttons or they can be added to the drop-down list box on the custom command toolbar. If the user selects a custom toolbar button or selects the name of a custom command from the list box, the associated functionality is performed. All custom commands are associated with a session. If you wish to create custom commands that will be shared by your sessions you should create them for the default session and then create your sessions afterwards.
...