The latest version is in my editor project at https://gitlab.com/gushogg-blake/edita-release. It will apply changes but it's just the minimal functionality at the moment, there is no feedback after you press the Replace all button. My process is to use the editor and write whatever I most need on it right now so not sure when I'll get round to fleshing it out.
Ideally other editors will take inspiration from it and add their own implementations. The code is available for reference here and I'd be happy to go over it in detail with anyone who wants to: https://gitlab.com/gushogg-blake/edita-release/-/tree/main/s....