Cluster graphs have many node options described here. The sidebar is not the only way to access these options.
Some options have mouse shortcuts. For example, in cluster graphs with edge indicators, simply clicking the edge indicator arrows will toggle the corresponding “Show Edges” option.
By default, double click will toggle the “Show Children” option, expanding and collapsing clusters. Double click can also be configured. Graph settings are accessible through the shortcut on the graph window and also from tools->options->graphs (Windows) or Understand->preferences->graphs (Mac).
Double click can toggle show edges in, show edges out, or a combination that tries the first valid option for a given node. For example, if double click was set to “Expand/Collapse Clusters Show/Hide Edges Out” then double clicking on HunkWidget would turn off edges out (because HunkWidget is not a cluster) but double clicking on Header would expand Header (because Header is a cluster).
Keyboard shortcuts can also be assigned. The shortcuts are local to the Graph Window so they don’t have to start with Ctrl.
The “Inverse Selected Nodes” action is only available when assigned a keyboard shortcut and inverts the current selection.