I think the reason why your question has remained unanswered for a while is that are educators aren't sure what you mean by "Narrative Art." I have been thinking about the dual term you mention and have concluded that you must mean the art involved in narration by Sir Walter Scott. Therefore, what you are really talking about is plot. Plot is the instrument of narration, and Sir Walter Scott is certainly very good at pursuing this art!
Let's look at the elements of plot in Kenilworth and decide how they could truly be called narrative art. The first element of plot is exposition, where we learn about the characters and the setting in the story. The setting of course is Kenilworth, in the England of Elizabethan times. We learn about the characters such as Tressilian and Varney and the mysterious lady Amy. The next part of the plot is called the conflict or the inciting incident. In Kenilworth, the conflict begins when we learn that Amy might be a prisoner at Kenilworth. It is after this moment that the rising action begins, when Tressilian is in the inn (thinking about his former sweetheart, Amy) and many other people at the inn are interested in Amy's fate as well. The rising action is all about finding out the truth about Amy. the rising action comprises most of the novel. We hear a lot about Amy's true husband who was named the Earl of Leicester, who is actually in favor with Queen Elizabeth and trying to stay in favor with the Queen. During the rising action as well, we find out that Varney is actually the villain in the novel. There are many lies told. Elizabeth threatens to come to Kenilworth to meet Amy. Eventually, the Earl of Leicester actually tells Queen Elizabeth the truth about his actual wife. Meanwhile, Varney has a murder plot to kill Amy. The climax is the height of the tension in the story. The climax happens when everything seems to be resolved, but Varney carries out his murder plot by making Amy fall to her death through a mysterious trapdoor. The falling action and the resolution of the plot is the part when the tension is over and the characters' lives return to normal. In this story the falling action and resolution take place at the end, of course. It is actually very interesting! We learn that Varney commits suicide in prison and Tressilian is held in favor in Elizabeth's Court, but is eventually killed by poison. What a strange falling action and resolution!
I would say that the narrative art in this plot by Sir Walter Scott is that there are interesting things that happen in every single part of it, even the falling action and resolution! There is always something exciting happening, and not necessarily just in the rising action. This is a part of Sir Walter Scott's art in narration. Sir Walter Scott keeps us interested utill the end.