I'm aware that this is a somewhat older thread, but for those among you who can't find the checkbox, that's because it's no longer a checkbox.

I've uploaded a screenshot.


PS: The screenshot may be from GOG Galaxy, but it uses the same interface as on the browser.

You're the best! Thanks so much for this reply!

A little update. It looks like there have been changes on the website and even instructions from GOG are out-of-date.

Now to unhide a game, go to your games library on the website and on the left corner just above the first game you will see a pull down boxed labeled "My Collection" click that and you will see "My Collection, "Updated", and "Hidden" options. Click hidden and it will show any hidden games where you can unhide them the same way you hid them in the first place.

There is a way to do it from Galaxy as well, by changing the filters. But I don't use that so I am not certain on how. I suspect that is the method GOG now gives on their own help pages.

https://www.gog.com/forum/general/how_to_unhide_games/post16
Literally two posts above you, dude. From May 2015, as I may add.