When the add button failed to work the first time and nothing I did (I did find a few errors) fixed it, I started over from scratch. The Add button still does not do anything. I check the bindings and connections and everything looks like I expected.
I think the chapter needs a LOT more detail and screenshots, because I’m obviously missing something every time I try this exercise. I think for now I’ll move on and come back to this later.
Perhaps someone has a suggestion meantime?