?? I read your answer 5 times - and I'm still confused.
(Yes... I know you're rolling your eyes and smacking your forehead - and you probably have every right to.

)
Like I said, I always felt I was missing something very obvious and your answer seems to indicate that I was right... and that unfortunately for the time being, I will keep missing it.
From your answer, it almost seems to imply that the 'import/export' function is unnecessary. That all I have to do is copy/paste. Yet that doesn't seem quite right. If it was, why would that method (imp/exp) be explicitly detailed in the 'moving from one computer to another' instructions? It would seem to me that the import/export would not only address the database, but also the config of Calibre (extra columns etc..). And that simply copying the database would not duplicate that.
Or maybe I don't quite understand the concept of 'Library' as it is used in this context... I simply have one folder with an enormous amount of books.
Look, I really am sorry about bothering you all about this. I am relatively certain that creating a new folder and 'importing' the data will work just fine. It just bothers me that I don't quite understand the logic process.
Usually I would expect to be able to import the 'old data' into the newly created 'default' folder. The fact that I can't do that is confusing to me, but that it is my problem.
Thank you so much for your attempt to explain it, but I think I need an 'Idiot's version' or perhaps an Idiot idiot's version...