How do you remove silicone without damaging surface surface is wood varnished?

There are several brands of silicone remover on the market today, (screw-fix has one) If you decide to use one of these products, pay close attention to the hazards and warnings.

As for myself, I would use a razor blade to remove the bulk of the material, (very carefully skim the surface) now hold the blade perpendicular to the surface and "GENTLY" scrape the surface, if done properly you will remove the silicone and a micro layer of varnish (without removing the whole layer of varnish), keep in mind the silicone could haved stained the varnish and spot removal of the finish must be reapplied.