I really like this idea and this would be especially helpful for macro controls and modulators because they can get quite complex.
I came here from Ability to create your own Help Pages for devices and I think this would tie in quite nicely there if the help window would show these annotations. However, it could be quite difficult to implement an algorithm that distributes the annotation over the help screen, especially if they become longer.
Should the inspector annotations become their own feature request? Or if @chaocrator agrees, we could rework this one because personally, I don’t see how a dedicated device would offer any advantages over annotations in the inspector panel.