To preview playback, use the play buttons located in the toolbar at the top of Sound Cue Editor window. For more information about the toolbar, see Toolbar.
The Play Cue button plays the entire Sound Cue, and the Play Node button plays the sound from the selected node. (If multiple nodes are selected, the Play Node button is grayed out and unavailable.) While a Sound Cue is playing, to aid in debugging, the wires of currently active nodes turn red. This makes it easy to follow the Sound Cue's construction in real time.
You can add an audio node by dragging it into the graph from the Palette.
You can also add a node by right-clicking in the graph and choosing a node from the context menu that appears.
As with other node-based editors in the Unreal Editor, you can type text in the search box to dynamically filter the list of nodes that appears in the context menu.
If you have a node in the graph, you can add a new node by dragging a wire off the existing node's pin and choosing a new node from the context menu that appears.
For explanations of the nodes available for use within the Sound Cue Editor, see the Sound Cue Reference.