Any object in your simulation simulation can be made invisible (so it is not seen when the simulation runs). You can do this so that you can remove clutter from the screen.
For example, you might include an Activity to control Routing that does not really exist in the situation you are simulating (perhaps because the Work Items are intelligent and make their own choice about where to go!).
To make an object Invisible, click on the Object, go to the Graphics tab of the Ribbon and tick the Invisible check box.
If you want to view your Invisible Objects when editing your simulation, you can click on the Show Routing Arrows icon.