Art Lindquist wrote:

A friend of mine has a table he wants to finish, in semi gloss polyurethane.
He has about 3/4 gallons ea. of satin and gloss both the same brand. Rather
than spend the money for semi-gloss and have more unused material. He asked
if he could mix the two and come up with something in the middle of gloss
and satin. It sounds possible, but I have no experience with such a mix.
Has anyone done this before?

Probably be fine--just take a sample of each and try it on similar piece
of scrap wood before committing to the project.