I don't know if this will help anyone to help me (if there's anyone left who is willing to try), but somehow not only did I put stuff on the SD card at one or more times (there's 24.08 GB available now on the 32 GB card), but I've also managed to save stuff in both Google Drive and Dropbox (for some reason it's easier to access Google Drive than Dropbox. I wonder why?
). But I feel sure that the files now on those cloud drives were saved there to begin with, and not transferred to those drives from some other source, like the internal storage. I'm wondering now if that is why there are quite a number of files on the SD card. But now I don't remember how I did it, if that is what happened.
And will the phone look for apps if they are on, say, the SD card, only if they are in internal storage, or in both places? Maybe there is a setting for that; if so, I either haven't come across it yet or didn't understand the significance of it.
Right now I'm going to install Calibre Companion, that Dr.Ohh mentioned on this thread (post #31), and see if I can't at least transfer all of my books to the SD card. That
should free up some room in internal storage, but as I mentioned in one or more other posts, when I
uninstalled 3 or 4 apps, nothing changed in at least the readout of the total GB used or of the percentage used. And if CC did work, I'll only be kicking the can down the road, but right now I'll settle for something that will work for even just a little while.
Thanks, again, to all who have helped. Let me see what happens now with Calibre Companion; it looks from things said on this thread, and in another one in this forum that Moon is available only as an app, which, of course, I won't be able to install.