I've searched and searched on Google as well as through articles here and could not find a thread that could say with certainty what it means when your glider winks at you. I even ran into one where people were suggesting to bring the glider to the vet to make sure there is no infection or scratch on or under the eye...
Well! I'm not saying don't go to the vet. Go to the vet! If you ever feel that there could be ANY possibility your little floof is sick or hurt. It's better to be safe than sorry.
But! I've received a clean bill of health on both of my babies but both still love to wink at me occasionally. Especially when treat time comes around.
So after searching, I came across an article about "Common Gerbil Behaviors" that included a section on winking. Here's the link: https://www.petcha.com/12-strange-but-common-gerbil-behaviors/
But the short and sweet (too late) is that if it's the same as Gerbils behaviors at all, it simply means that they are content/being submissive when they do. The article suggests that you should wink back at them kind of like a, "All is well.", signal to them.
Here's to many more winks!