In early days games could be bought either on your console or Steam. And now every major publisher has its own platform. If you want to move games from these stores to Steam, here's the solution.
This is autotranslated version of this post.
SteamGridDB will help to export games from Origin, Uplay, Epic Games Launcher, Blizzard Battle.net, and GOG.com to Steam.
In addition to access to all games from a single library, you will receive all the benefits of Steam: the ability to play on the TV, access the community, connecting various controllers, play on various devices.