I’ll prob get downvoted for this, but paste the instructions into an LLM and have it assist you. misread OP’s comment

As for user.js prefs potentially aging out, arkenfox updates very rarely (once every few months IIRC), so the present user.js should be fine for a while until someone inevitably forks and maintains mull.

Personally I had to change mulls prefs(‘<…>’) to user_prefs or vice versa to get it to work.