I dont know why this topic don't make a buzz..... but i have a solution, the problem is, you need put each game manually....
- Open xbox cloud gaming in your browser, sorted by "all-games"
https://www.xbox.com/fr-FR/play/gallery/all-games
- Right click on your game you want add and click "copy destination url"
- In your launchbox
> Windows section > right click and ADD a new game
> Search information of your game
> In "launch" section put the URL of your game in xbox cloud gaming.
> Add media
save and enjoy
Its working, but is not the perfect way...