However, getting your software to use those directories can vary. Depending on your game launcher of choice, you'd have to figure out how to tell it to install games to your desired location. If you have a more concrete example then I might be able to detail this further.
I do use Steam a lot, and I know they have tools for it, but a bunch of my library is installers from GOG and from Devs directly, which I'm sure I'll struggle to get working in the first place.