Just so you know, when you "add a directory" to Experience, all you're doing is linking the program to a directory location on your drive. If the directory location doesn't already exist somewhere on a drive that is connected, it won't show up in the GeForce Experience locations list. In other words, when you hit the "Check now" button in the Preferences tab under "Games", it's going to go through whatever drives are physically connected to your system and locate games that are installed and supported, and add them to the locations list. You can install a game to a connected drive, then manually direct GeForce Experience to it by hitting the "+", then browsing to the game's directory location.
There are no games installed in the Experience program or program folders, only settings for games that are installed elsewhere.