This is a feature of Ren’Py, a software for designing visual novels. I’ve played a few games where it fast-forwards through text you’ve already seen and highlights choices you’ve already made. The good thing about it is that it’s almost always an invisible part of the design until you replay; super non-intrusive.
It’s nice for a victory lap after you’ve already completed the book, but it also kind of fosters a gamification of the story, where you’re just trying to see all of the content rather than get immersed. Ren’Py visual novels are explicitly game-games, whereas with ChoiceScript the line is a little more blurred, probably leaning more towards novel than game.
Personally I’d just love more ChoiceScript features. I respect the fact that it sticks to its design goals, but a little more room for variation would be nice. I dare not mention the other major feature that most people ask for as that discussion is a little played out and we know what the answer is. Even getting implicit control flow as the default option is an uphill battle as there’s some hang-up about it maybe being slightly more difficult to spot a specific type of bug sometimes for some people. I doubt we’ll see much traction for implementing a massive change like choice highlighting, especially when we can’t even change the colour of the text natively lol.
You can totally add audio files. It would massively balloon the size of the game, and it’s a massive amount of work to effectively release a 300,000 word audiobook alongside your 300,000 word interactive fiction book that also takes into account all of the different variations of every single scene, but it is, in the most technical sense, possible!