A little while ago I wanted to make a change to my entire story, implementing custom character names. This was extremely frustrating having to go through 50+ chapters and edit each to use the variables instead. It'd be awesome if there was some kind of find/replace that works storywide or an entire story export/import function so authors can make changes like this in their favourite text editor. Obviously this would be capable of screwing up a story if used incorrectly though.
Find/replace can be dangerous as discussed here. For the special case of introducing a new immersion variable, I think a function to up- and download stories would work better. There is a suggestion about this from the Reader Suggestion story
Indeed, which was why I was extremely careful and thought about the special cases when I did it myself, but I still had to go through every chapter one at a time, copy paste find replace copy paste update silent save. I don't want to have to do that again!