Never. But I can see where it may be useful, eg cutting high end planking/flooring, where the ends need to butt up perfectly (and where you do the marking on the bottom of the material, of course).
I’ve been looking around online for a video that shows why you would use it but can’t find anything. Does anyone have a link or some pictures on how/why it’s useful? I’m a new TS55 owner.
Used it 4 times when I wanted some mitered chests to match perfectly at the top corners. They were plywood. The veneers matched perfectly. Nice feature when you do not want gaps showing.