It would be nice if the "already in collection" note while browsing/adding games showed the format in which it's in your collection - "already in collection (Digital (Steam))" or something. I know there are some games I own in multiple formats or from multiple digital sources that I missed while adding my GOG games because it said they were already there and I didn't think to check.

Also, is there some way of getting the game details from the browsing/adding games screen? If I want to see what games are included in a compilation game, for example, I can't figure out a way to do that without adding the game to my collection and then clicking on it. If I click the game from the games list, it shows me the site stats for the game, which is nice, but not always what I'm after.

You can click on the "already in my collection" note and it'll take you to your collection, filtered down to just that game. It's not ideal and requires a bunch of extra clicks to achieve what you're after, which is to add games for the missing formats. You could open the link in a new tab, which would help, but still doesn't quite solve the problem. I only mention it as a workaround for now until a proper solution is in place.

For a proper solution, I think some sort of tooltip when you hover over the link might do the trick. The only issue with displaying the platform / format is that you could have it on multiple platforms / formats and I'm not sure how that would look. It's a good idea though, so I'll throw it on my task list and take a look at it.

Regarding the compilation games, I do plan on adding support for those on the Game Details page (i.e. the page with the site stats). I haven't quite thought through that feature, so if you (or anyone else) has any ideas, definitely let me know. I figured I'd at least display the fact that it's a compilation game (icon, text, etc) and somehow display the games within it, each linking to their individual game pages.