Good idea; I was able to change the value of js.composer.create_pm (back?) to Reply and achieve the same functionality as before, although with the new envelope icon on the composer “send” button (which is fine). @Osama may know of more changes that impact this theme component that we haven’t unconvered yet, given this commit and potentially any future work in this area:
https://github.com/discourse/discourse/commit/c9923a3e3e9abd318140f77f06d6472ef28b262b