A few sites now reporting details of some changes in the latest Steam client beta.
http://www.pcgamesn.com/everybody-panic-steam-different
It’s now possible to hide games from your Library - a tool for those who would prefer to pretend they never did buy Sacred 3. To do that, you'll want to head to the Set Categories menu for the offending game and tick the appropriate box.
http://www.pcgamesn.com/everybody-panic-steam-different