@Override
	public void actionPerformed(ActionEvent e) {

		// Now fire off an event to tell any subscribers to perform the increment.
		FVEvent incrementEvt = new FVEvent(EventType.INCREMENT_AND_ADD_SELECTION, 1);
		eventListener.send(incrementEvt);
	}
The down arrow should move the selection down one row. Just fire off an event to tell the
viewer to increment the selection, which may involve an adjustment to the viewport.
Ghidra/Framework/Project/src/main/java/ghidra/framework/main/logviewer/event/ArrowDownSelectionAction.java