I realized today when adding other features that the rules editing was broken for 1.12 and older. I had been testing on 1.19, so I didn't notice. Apparently Material.WRITEABLE_BOOK isn't valid before 1.13.

So I added a flag so it can detect if it's on 1.12 or older, and then the edit command will use a line number based system like the original version. See the documentation tab for details.