Adjust an oven rack to the lower-middle position and preheat to 350°F. Spray a 9×13-inch baking pan with non-stick spray. Line the pan with two overlapping pieces of foil or parchment paper, leaving overhang to act as handles for lifting the bars out of the pan. Spray with non-stick spray.
Spread the coconut on a baking sheet and bake until the outer flakes just begin to brown, about 4 minutes. (Keep a close eye on it – coconut can go from slightly browned to burnt in a matter of seconds.) Set aside.
Melt the butter and combine with graham cracker crumbs in a small bowl. Toss with your fingers until the butter is evenly distributed. Press the crumbs evenly onto the bottom of the prepared pan.
In order, sprinkle the walnuts, chocolate chips, white chocolate chips, butterscotch chips, and coconut over the graham crumbs. Pour the condensed milk evenly over the entire dish.
Bake until the top is golden brown, about 25 minutes. Cool in the pan on a wire rack to room temperature, about 2 hours.
Remove the bars fromthe pan using the foil or parchment handles and transfer to a cutting board. Using a sharp knife or bench cutter, cut into 2 by 3-inch bars.