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In the BPMN viewer, manipulation of the returned illustrated flow is possible by using the following methods. On the left side of the viewer window there are three symbols. 
will zoom in on the flow with each subsequent click. 
will zoom out on the flow with each subsequent click. 
will fit the flow to the full window, if it has been zoomed in or , zoomed out or moved. Along with these controls, the user can left-click and drag to move the flow within the canvas to the user desired position.
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