Hi, Rich!
Technically, registration banks are no more (and no less) than files on either the internal "hard disk" or the pen drive connected to the keyboard. Despite the interface on the keyboard being somewhat clunky, all the operations you are doing are essentially the same as the operations you would do on a computer with files.
When you save a bank with a different name, it's the same as doing a "save as" operation. You create a new file with the saved contents, and the old file is not affected at all. But beware of doing intermediate "save" steps, as they will overwrite the original file (as would a "save" operation on a computer).
Since creating an empty registration to start with is somewhat... complex (pressing a key while turning on the keyboard is not something you want to do as a "normal" operation), one alternative many of us use is to do this once, and save the (empty) registration as a file with a significant name like "Blank" or "Empty". This way, when you want to start with a clean registration, you just select ("open") this empty registration, start working, and save under a different name.
I hope this clarifies it a little bit for you. Regards!