This feature can help you simplify your graph and avoid overwhelming the user when featuring a large amount of nodes. You can use Source Focus Node and Target Focus Node fields to assign one of two Focus Node states to each node:

• 1 (true): the node is a Focus Node. User can expand non-focus nodes below it by clicking it.
• 0 (false): the node is not a Focus Node. 

This field can be used to determine the node behavior depending on your selected settings in the Navigation section of the Format Visual tab. 

• Initial Display Mode: choose if the initial view displays all nodes or only Focus Nodes. Note: can also be adjusted on-the-fly with an optional toolbar button.
• Initial Node Expansion Level: select how many hierarchy levels are visible in the initial view.
• Node Expansion Radius: select how many levels of hierarchy will be expanded when the user clicks on a focus node.
• Initial Expansion Direction: select the direction in which the nodes expand (source->target; target->source, or both). Note: can also be adjusted on-the-fly with an optional toolbar button.
• Initial Explore Mode: choose what happens when the user clicks on a focus node – expand or highlight. Note: can also be adjusted on-the-fly with an optional toolbar button.