Does it make sense to apply a (Minwax) wax paste on top of a polyurethane/stain finish?
You can wax it if you like, but it is not needed. The only time I would add wax if in the case there is slight imperfections like dust in the finish, and you would like a smoother finish. Wet sand the top with 400G wet sandpaper and work it up to 600 then 800. Then apply the paste wax. The trick will be is, if you have enough finish to do this much wet sanding. I do this with lacquer finishes but there are 3 or more coats in place to work with. This leaves a glass smooth surface when done, but it leaves a matte/satin sheen.

There are tutorials on "rubbing out" finishes online. This is where I picked up on this.