I admit, I've become addicted to seeing the File Libraries as part of Windows Explorer. Libraries have been a great way to help organize files and then access them quickly. But, after a Windows 8.1 installation or upgrade, you'll notice that the Libraries are no longer available. Microsoft didn't remove them completely, just chose to not enable viewing of the Libraries by default.
If you want them back, do this:
Open Windows Explorer, click View on the menu, select Navigation Pane, and then put a check next to Show libraries.
However, Windows 8.1 also contains another Windows Explorer option for helping you organize your files and folders, and I submit that it's a much easier way to consolidate file locations. Windows Explorer includes a Favorites section where you can drag and drop your most commonly accessed folders. After creating Libraries for a long period of time, even those can accumulate and become unmanageable. Try sticking your most used Libraries into the Favorites area and organizing that way.