Is there a Scoville scale for "coldness" (e.g. mint)?
There are thermal sensation scales, and they are applied in food research too, although their primary use tends to be focused on clothing or environment. They tend to be categorical rather than ratio scales, and don't depend on the presence of a single compound the way scoville does. Despite checking several likely sources (a book on neurogastronomy, a thesis on measuring the perception of food - mostly focused on texture, but also discussing thermoreceptors) I didn't find a mention of a specific culinary scale that measures menthol concentration. 

Instead of a specialized scale, industrial users of menthol products seem to simply use the relative menthol content, such as selling an essential oil that with "60% menthol". And the general public doesn't seem to have created a cult around menthol content the way it has done for capsaicine content - personally, I know more people who care for the scoville number of the chilli they are eating than people who can tell the difference between spearmint and apple mint. 

I suspect that, while creating such a scale is possible, nobody has bothered to. And even if some food scientist did do it, it doesn't seem to have caught on, especially outside of professional circles.