Honestly, the sorting and categorizing system for steam is good.... if you have 20 games, but at 100+ it's unmanageable.
Why not have have a "New Category" button, which pops up a window, and simply Drag'n'Drop your games (made easier with Shift+Clicking) into that window, and then everything is in that Category, saving roughly hours to both the default and Depressurizer.
I mean a lock system wouldn't be hard, It would work as a category, which is your "locker" which shows you how long it's locked, or even take it a step further with a "self-ban" feature for those that need to eliminate to temptation to play in work hours.
I love steam, but the program itself really needs a ton of work, Big Picture needs an overhaul in terms of customization and performance.
Even Grid mode could use options such as a Categorized View which should sort it akin to list view, which breaks the grid at each category, even a tile mode could work too.
Still most of these problems stem from having a 100+ library (I'm inching in to 600 myself, and Fuck no I don't have the will to sort em all out).