You can use the up/down and left/right arrow keys to pickwalk in the Node Editor as you would in the scene view and the Outliner. Use the left/right arrow keys to pickwalk through the sibling nodes, the up arrow key to pickwalk through the parent nodes, and the down arrow key to pickwalk through the children. The corresponding nodes are selected in the Node Editor, scene view and Outliner.
See also Define a custom pickwalk hierarchy.