The question is now long and more time passes, the more the situation seems to degenerate. We count the number of possible launchers for a PC player: Steam, Origin, Battlet.Net, Epic, Bethesda, Uplay (lol), GOG, itc.io. Seven, always if we have not forgotten someone. Too many, especially when you do not remember in which account a certain game is held. Thanks to a tip of How-To GeekHowever, we find that a solution is possible and finally has a name: Playnite. This is a universal library, compatible with all the launchers existing in the world and, above all, open source. Once the application is launched, Playnite will automatically scan your PC for each individual game, adding it to the library (clearly you can also do this manually). Obviously it does not end here. When you decide to start a game, it will be Playnite to open the client needed to start up, allowing you not only to have all your titles at hand, but to start them from the same, unique launcher.
Try it, we are doing it. You can download it here.