I’ve somehow ended up with both the Beat Saber demo and full version. I’d quite like to remove the demo from my library, but I can’t!216 votes
As noted below, if you hover over an app’s tile in your library and click the three dots in the bottom right corner, you can select uninstall. This will move the item from the Apps section of your library to the Not Installed section. The Not Installed area hosts all the apps that you have purchased or downloaded previously, but are no longer downloaded and installed on your device. Utilizing this uninstall feature should allow you to remove the Beat Saber demo from the Apps section and only have the full version of Beat Saber listed there. Hope this helps!