The term "panning" is used to denote shifting the entire diagram (including any parts that may not be showing). This is for ease of viewing only - it is not a permanent change.
Clicking on the "Pan On/Off" button at top right will toggle the panning function. When it is checked, the cursor will change to an open hand, and you can then just drag the cursor in the direction you want the diagram to go.
While the mouse button is pressed, and panning is taking place, the cursor changes to a closed hand.