RedQuill review
RedQuill makes it possible to keep two versions of a story after the plot reaches a choice. Its Fork tool copies the draft up to a point you select. The original stays in your library, and the new version can take the story elsewhere.
Keep a second version of the story
RedQuill’s guide describes Duplicate Story for making a second draft and Copy and Continue for generating a new chapter as part of the copy. Each fork is a separate story. On iOS, NovelX offers version history for chapters written in the app, so you can restore an earlier draft of the same chapter.
Check what the plan covers
The Quills page lists allowances for chapter generation, paragraph edits and narration. It also lists EPUB and PDF downloads. The terms say the daily Quills allowance resets each day and direct subscribers to the billing portal to cancel before the next period. The rules require adult users, bar mature depictions of minors or real individuals, and require permission for material you submit.
Anabel’s take
I'd duplicate the draft before rewriting a chapter I might want to keep. If I already knew what should happen in the next chapter, I'd start with Copy and Continue.