Updates to Files On-Demand on macOS

Rick_Baumhauer  It's good to know that's a possibility, but at this point I don't see the need. With my account deleted from the system drive, that volume is now only 34% full - plenty of room on which to store more apps.

Yes, offloading large files created by music software (Sibelius, in my case) to external storage is something I've been doing right along - creating directories on the external HD and using symlinks to point to them from within my home directory. I never had a problem with that, except that the external HD is slow. I don't think that was ever a problem when creating the files to begin with - to create a sound file, Sibelius plays through the score at high speed, but it's still a fairly slow process that I don't think had much to do with the time required to write, since the app probably buffers everything until it's done playing back and then writes it out, which took a few seconds but nothing too painful. Audacity may have been a different matter. Anyway I have everything on the external SSD now, all of my sound files in subdirectories of the Sibelius working directories with no need for symlinks, so I'll see soon enough whether I gain any speed this way. The SSD is still only 11% full, so I have lots of room to work with.

If I ever need to clone my system disk onto the external SSD, temporary space could be a problem, you're right - I'd (just barely) be able to fit everything now, but that is likely to change. I could also use the HD as of now - but I'm trying to figure out a way to extend my Time Machine partition on the HD to take up the entire drive, and put everything that's on its data partition on the SSD. That will effectively close off that route unless I bought another external HD.