I think this question has been answered before, but does anyone know of a safe stripper that will remove varnish, but leave the underlying epoxy alone? I don't want to do much heavy sanding, because the epoxy is thin in places. Thanks.

When I used to refinish furniture I'd start with alcohol and steel wool. Try that.

If that's not working I'd progress to something like 3M Safest Stripper, a water washable low toxicity stripper.

Work outside if you can, and wear gloves and eye protection.