I would guess that someone has done this, but I have not seen it yet if so. My plan is to do a removable wasteboard like David Westley did here: Wasteboard hell - #19 by DavidWestley and then have a hole in one side of the board for when/if I want to do some work on the end of something long, like engraving the end of a single piece cane or maybe putting in dovetails with a dovetail bit. This would let me cut something taller if I could clamp it in place.
Has anyone made a variable height wasteboard so taller things could be cut? I really don’t know how often this would be useful, but the flexibility would probably be nice for some applications. Getting it rock stable would be the hard thing of course.