>>150081991
Graphic novel doesn't have a set definition so it's complicated. Some say it's a comic book with a spine yet some would consider it one continuous story like an actual novel. So it's going to be hard to track down where this started but a Graphic Novel is what Eisner wanted to do with A Contract With God so could be a good place to start (even though you can debate if it is a novel since it's a short story collection)

Single issues collected into a book might be called more like a "Collected Edition" which sounds like what you are asking. Look here
>https://en.wikipedia.org/wiki/Trade_paperback_(comics)#:~:text=In%20the%201990s%2C%20%22trade%20paperbacks,entire%20series'%20stories%20to%20date.

Marvel's Masterworks and DC's arhive editions start in the 80s but they were collecting books together before this, foreign countries used to get issues packaged together into one book as well so it's complicated. It's going to be confusing to pin down what you want to mean by "graphic novel" and pin down exactly what you mean by "started" I guess