Hey, you already can add custom inference actions by modifying the `actions.json` in the workflow folder. See also the discussion here #6.
That's "normal," and I've already noticed it in Apple Mail. The problem is that Apple is hiding the fact that you're currently in a view that accepts text. This prevents the safety feature (stream or paste iff the frontmost app's selected view accepts text) from detecting that you're actually typing or editing text in Apple Mail, leading to an opt-out. I haven't found a workaround yet. The only reliable method at this time is to ignore the safety check altogether for specific apps. Naturally, I'd like to avoid that, but I'm considering making it possible through an environment variable that needs to be manually populated. I find Apple Mail's issues here mildly frustrating myself 😅.