Capcom has updated Denuvo for this game. So they have to rebuild the trainers to get around it again, as there's all sorts of anti-cheat checks added.
Yes, same as adding any other item, especially if you know the ID codes. looking on the Editor discussion would probably be best :-P
Which item are you looking for?
I would recommend just adding part breaker 3 and such using editor, and a ton of damage to your weapon. You can clear all "4" stages and complete the event around 10 minutes.