One of the features of Exact Synergy Enterprise is that you can share information and view information on several locations. Not all information shown in the screen is always relevant. It also may be the case that you need more space on your screen because the monitor does not show the full screen.
In these situations you can hide the left menu. This can be done via the arrow that can be found in the top-right of the left menu:
When the menu is hidden you can show it again by clicking the same arrow: