I started a new topic for you since this is really off the sign-in topic.
Export is only from SketchUp to Layout. There is no path the other way. There are extensions to do very powerful splines in SketchUp which can then be viewed in Layout, though. Have a look at Fredo6’s Bezier Spline available free from the sketchUcation store.
The design paradigm we hold to is that drawing in 3D should be so easy that you start there, then use LayOut to communicate via construction documents or catalogs or paper in 2D. We probably could have made it easier to do this, but it defeats the process. Try it. We think you’ll be much faster/better if you do.