It may dry faster but I do not think it will cut back on the gloss much.
If you let the varnish dry for a week or more (the longer the better) then use a synthetic scuff pad to dull the finish. Then to bring it back to the shine you desire use a polish.

Here is a link that might be useful: http://www.superwoodworks.com

Satin finish is made by adding a dulling compound---if you let satin varnish sit for a couple of weeks, that compound settles to the bottom.

You can buy that compound at most paint stores. Mix it in the can and no need to sand later. Sanding---with 000 or 0000 steel wool is one way to dull a shine.

garrysmith,handymac
Thanks for the link and info.

Just thinned the varnish a little, as was too thick.
Its been sitting in the can at least two years, about 1 third ful with a good hard scum on top. pour into a plastic container. will go to hardware and pick up an empty quart can to re-store left-overs.

Will follow your advice. will leave for a couple of months as is, and than decide the sanding thecnique to use, to dull down. In the meantime family will live with it.