Preheat oven to 350 degrees F (180 degrees C). Place butter in 13 x 9 inch pan and melt in oven. Swirl to coat bottom and sides with butter. Spread crumbs evenly over bottom of pan. Layer chocolate chips, butterscotch chips, and nuts over crumbs. Pour condensed milk over nuts. Sprinkle coconut over condensed milk. Bake until edges are golden brown, about 25 minutes. Let cool.