Quarks.install("/Users/crucial/Library/Application Support/SuperCollider/Extensions")
or better yet, keep them where you can easily find them:
Quarks.install("/Users/crucial/Documents/SuperCollider/classes")
or just go to the Quarks.gui and click to add a folder.
You select with the standard operating system dialog.
> To me, Quarks are of a different category than just files I chuck into my extensions folder without specific quarks description file.
Quite the opposite.
That was in fact the whole point: you can add any folder,
you do not need a quarks description file.
It does not need to be on github,
it does not need to be in any community directory.
It does not need to be in git at all.
You can download anything you like and simply add/remove that folder using the gui.
Or just add one folder where you like to keep stuff and add that whole folder.