The history of the Undo Action should start zero when opening a new graph and node include node select actions.

Currently in the "Show sea of nodes" view you can press Undo once before doing any changes. In the "Show control view graph" you can even go back many times when opening a new graph, ending up in wired stated of the graph (see screenshot).

Further selecting a nodes is also added to the history. You can click on X different nodes in a row and then go back X times in history. Because the selection is not restored, for X steps back nothing happens.