I designed a class without engines by accident, and even made 2 ships. Now I want to retool my shipyards for a new class with engines. When I go to "Shipyard Complex Activity", however, only the original class is in the drop-down for the Retool for Selected Class activity. I've create a couple other classes, and nothing else shows up. What am I doing wrong? The Design Class window doesn't seem to have a "Save" button; it seems to save-as-you-go.