'Reapply Layout' resets the positions of the nodes. Note that the Spring layout uses random positions to start and will not result in the same layout every time.
Use the + button to add a new child node to some node.
Click the 'Pencil' icon to enter 'select' mode, then select several nodes. Click the canvas to exit.
Click the 'Home' icon to zoom out and see all the nodes.
Use the undo/redo buttons to undo and redo deletion/addition operations