Loft command doesn't show preview button

I am using Rhino 6, windows version.
The Loft command doesn’t show the preview button. Is there a way to add preview to the choices?

It previews by default. Any change you make to settings, should be able to be seen. If you see no change, put into shaded mode to see isocurve structure.

Thanks for the hint, I have seen the preview button in a video, probably it was recorded with Rhino 5