Combine cake mix, butter, brown sugar, and eggs in a bowl. Beat with an electric mixer, scraping bowl occasionally, until well mixed. Stir in peanuts and toffee; spread into an ungreased 9x13-inch baking pan. Sprinkle chocolate chips, butterscotch chips, and coconut on top.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, 25 to 30 minutes. Cool on a wire rack and coat with frosting. Cut into squares.