I think that the most comfortable way to use it is with an undo tree visualizer plugin. But if you want to only use the defaults, you have g- and g+ to traverse

I think that the most comfortable way to use it is with an undo tree visualizer plugin. But if you want to only use the defaults, you have g- and g+ to traverse the undo history in chronological rather than logical order, :earlier and :later which do the same but take a time argument like 15m, and :undolist plus :undo n which take you to a specific node.