The Graph is where you arrange your conversation flow and connect the Agent blocks together.
In the user preferences, under the Graph Gestures section, you can choose between Mouse and Trackpad gestures.
Select: Shift + Left click drag
Zoom: Ctrl + Mouse wheel
Pan: Left click drag or Mouse wheel for vertical pan and Shift + Mouse wheel for horizontal pan
Select: Click + drag
Zoom: Pinch
Pan: Use two finger