I have over 270 games and can't remove the already owned games by filter like I have been able to in the past. It's making it impossible to buy more because I can't keep track of what I own. I had to make this account for the forum because my game one uses some of my real name, which I don't want used. Neither have the option...

It's not a bug, it's a feature :P

Middle click on a game in games catalogue, check if you already have it, and then add it to your basket or not :P

Games will show already owned on the game page and during check out.

I find it weird how people can't keep track of what games they own - I wouldn't be surprised if most of them don't even own that many. Even without GOG telling me what I've already purchased I pretty much know the titles I own here, and that's with some 254 games.

Also, how difficult can it be to check your account's game list? Just throw it up on a second tab in alphabetical order and have a quick glance if you're unsure and/or simply check the corresponding gamecard as suggested.