[Atherton25]

With old stories, I do essentially with JimmXinu said. I add a tag to the title (old) ... sometimes with numbers IE (old2) and just remove the URL. Then redownload the book as a whole with the current chapters. I actually have another tag #FFFREM so I can remove\filter them from my current FFF list when I'm highlighting stuff to update too, just to make it easier for the rare times I update that way.

If I really need to later I can take out the chapters in conjunction with the newer book and then merge books, but I rarely do something like that. There are several newer large webfictions like He Who Fights Monsters and Defiance of the Fall that regularly remove old chapters to allow for Kindle Unlimited, and it's just a fact of life. While it'd be nice for a way around this without adding another book, that's likely too much work on the backend, and it works the way it is now.