Another neat addition would be to merge games that have separate exe files for single and multiplayer, CoD Blackops for example, and just have it ask which one to launch when you click play.

It's make sense but GOG Team should be added some menu in install button in games like this (option with select from which one platform u want to install the game).

Perhaps a general menu option that lets you make a list of your preferred platform order so it would automatically choose the first one on the list for each game

Going to give this a bump.
Additionally, this would be useful for games that end up showing multiple times even on the same platform.

Happens if the game is split between a Single Player and Multiplayer entry (typically with Steam games) and with Deluxe Editions and GOTY versions of games.

+1 to everything mentioned.

Also, it would be cool if you could easily tell from Grid view which game is currently displayed. Maybe a small top-left or top-right triangle with the platform logo to show which platform is currently displayed as the main one if they do implement some kind of stacking/merging system.

You can already do this by going to the library view settings (rightmost button in the top center) > customise grid view > additional data.

I'm with you in preferring the store logo instead of the name. Especially if the combination of duplicate entries should be implemented the logos would make it easier to instantly get an overview instead of reading the names.

Also a +1 to the general idea from me.

Have not opened galaxy 2.0 for some time, and to my surprise this seems to have been implemented. I guess no one from gog bothered to update wishlist. But I'm not complaining, finally my ocd will let me use new client. Thanks GOG

I would be great if this could be done manually too.
For example: XCOM Enemy Unknown Complete Pack (GOG) and XCOM Enemy Unknown (Steam) with all DLCs bought.