If you're a fellow new user purchasing the Huge Bundle™, note that it doesn't automatically add the games to your itch.io library. This means that Galaxy (and the itch launcher) wouldn't have anything to scrape from in the first place if you're looking to display owned games.
Currently, a game only get added to your itch.io library when you go to the bundle page, then the bundle's downloads page, and then access the download page for that specific game. To quote the bundle's downloads page:
Note: Projects in this bundle are hidden in your library by default untill you first access them in order to avoid flooding your library. You can return to this page at any time to access any projects you wish to show in your library.
Note: We will be updating this page soon, we know it's difficult to navigate so many games. We know you want a button to add show everything in your library. No need to reach out. Any new games added to the bundle will automatically show up here. Thanks!
Essentially, the itch.io developers are putting out fires and screaming right now. I'd give it a while before thinking about integrating it into Galaxy.