You can use 
Rake  for faster navigation in the model. The rake icon on the symbol indicates that the appropriate element is decomposed and has an inner structure. Double-click the element with rake icon to open the internal diagram.
The rake icon is shown on:
- Call Behavior actions that can refer to another Activity diagram.
 - Interaction Uses that can refer to another Sequence diagram.
 - Packages that can refer to another Package diagrams.
 - Parts that can refer to another Internal Block diagram.
 - Use cases can be realized by other behavior diagrams such as Activity, State Machine and Sequence.
 
Rake icon on symbol
To hide rake icon
- Right-click the symbol and select Symbol Properties or press Alt+Enter.
 - Set the Show Rake Icon property value to false.