Various files scattered among several folders on my desktop, e.g. Dropbox, Google share, and Box. A paper on medulloblastoma might be found within "PEDS", which is within "BRAIN", which is sitting in a file called "my old dropbox", on my desktop. Alternatively, a medulloblsatoma paper might be found within the primary "PEDS" folder on Google Drive, which itself is within the "CLINICAL SITES" folder. Expect to find the same paper in both places, or maybe in a completely different location, or not at all. Papers are variously named (short title, institution, year, author, etc).
However, I can't say that I recommend this method of organization.