Note that excellent utilities like BetterTouchTool (https://folivora.ai) and Alfred (https://www.alfredapp.com) offer app integration of LLM tools (any model, not just ChatGPT) easily into any app. So you can select text in Scrivener, activate using key/mouse/gesture and they will do the model interaction for you . I do use these for quick rewording / alternative sentance structures etc., and the same interface works in Scrivener, Mail, LibreOffice etc. This IMO is much better than each app offering their own take on using an LLM.
AND even better you can run the models locally:
This means no data leaking, no subscriptions, more control etc. The quality of local models are rapidly improving by the week. LM Studio and a good local model plug into Alfred or BTT and so you can even work with them on the plane etc. I often program on a long flight, and having an LLM to use as an offline Google search is amazing (a rough and ready universal library). I do recommend a 16GB+ apple silicon machine for the best experience.