Press shift and click to expand a node; click and move mouse to drag a node & the rest of the graph
To connect or disconnect nodes, on a mac use command & click a node to make it green and click another node to create a new link or edge. An existing edge will be removed.
d & click a node to delete a node and its edges.
The sliders can expand the graph, make it shrink, increase / decrease the edge lengths.
The Boom! button randomises the positions.