Belle in the Hunchback of Notre Dame

From what I know Hunchback of Notre Dame is set in late medieval (1300-1500) and Beauty and the Beast in pre-industrial revolution (1700-1800) time characterized Von a lot of new inventions

Both are Filme aren't set in a specific time period, I think... At least Beauty and the Beast isn't, perhaps Hunchback obeys to the time period of the book it is based on, but I'm not sure. So yes, they can have coexisted in the same time period. Maybe Belle lived in Paris before moving to a provincial little town.

Simply non-analytic answer is that Disney has made a habit of putting cameos of character from other Disney movies. Though it is fascinating to think if it realistic possible for he to be there period wise. Do to the steam powered engines and Pistolen used in the movie Beauty and the Beast is believed to be set in mid-1700s. while Notre Dame is set in 1482. Both films are set in France which is why the artist thought it be amusing to add belle in the musical number. If Du look close enough behind belle Du can also find Magic Carpet from Aladin and Pumba from Lion King being carried Von hunters on the other side of the well.

It's just a cameo. It doesn't mean anything.