No. No problem. As long as both satin ans semi are stirred well prior to mixing.

Have you tried looking at straight semi gloss first?
Adding semi gloss to satin will give you a tad more shine but its almost not noticeable to the untrained eye.

Thank you for the quick response! No, I have not. Perhaps, mix one part satin to two parts semi gloss? Now that I know mixing is not a problem, I can experiment in couple test patches to see what combo looks the most appealing.

Im not exactly sure how they mix semi gloss to make it semi gloss. It could be as simple as part satin part gloss. But i would look at semi first before you get too far into mixing polys.

I'm adding some semi-gloss to my satin for a tiny bit more shine!

If, you want more shine, step up to the next sheen level. Avoid mixing sheens, you will complicate things if, you ever need to do a touch up or repair.