How do I workaround this new warning in Xcode 4.3.1: “Scene is unreachable due to lack of entry points…”?

You can just set an identifier. In Xcode >5 on the identity inspector on the right pane, you’ll find a field called “Storyboard ID”. Put any string in there, and Xcode will be happy again.

It just wants to know you could reach it (via that identifier) if you wanted to.