satin varnish streaky

Depends on what caused it. Best guess you either didn't stir the finish well enough to get the flatteners into full suspension or didn't periodically restir.

Best way to avoid that kind of problem is to learn to rub out the finish to the gloss you want.

This has happened to me, applying Minwax satin oil-based over gloss.

I found the satin did not adhere to the underlying gloss as well as the gloss layers adhered to each other.

I would lightly sand your topmost gloss surface to present a rough surface for the satin to adhere to.

And as others have recommended, stir well! Every 5 minutes while working. (My new can came with the flattening agent all settled to the bottom... getting it mixed again was extremely difficult!)

- Daniel