At the moment that tool does not exist, but it is on the list and will likely make it into the release of version 2.0. In the meantime, it is quite easy to do with native SketchUp.. What I do (see image attached) is copy both the top rail and the bottom rail and combine them into one rail (the top rail provides the bottom dado and the bottom rail provides the top dado. Be sure to make the copies unique parts immediately after copying them or you will end up changing the top or bottom rail. Once you overlay the parts you can use the SketchUp Outer Shell Solids Tool to create the final part. This works especially well with raised panel rails and stiles as shown in the attached image.