This is not an error but is something that I think it would help a lot on development if on future versions of Unity we could see the new Events we add to our Buttons on Inspector by AddListener delegates on script.
I found that because I’ve seen that although the listener is working on scene I couldn’t find any reference on the Inspector.
Yup. I would appreciate this as well.
Unity has said that the forums are the better place for feature requests (official post on the subject). You might have more impact if you re-post over there, maybe in the UI Systems section.