Prep the pan: Heat the oven to 350°F (175°C). Line a 9x13-inch baking pan with parchment paper, leaving overhang for easy lifting. Lightly grease the sides.
Make the crust: In a bowl, stir melted butter and graham cracker crumbs until evenly moistened.
Press firmly into the bottom of the pan to create a compact, even layer.
Add condensed milk: Pour the sweetened condensed milk evenly over the crust. Use a spatula to coax it into the corners if needed.
Layer the toppings: Sprinkle chocolate chips evenly, followed by nuts and butterscotch chips if using. Top with the shredded coconut, spreading it to cover the surface.
Finish with salt: Add a light pinch of flaky salt over the coconut to balance the sweetness.
Bake: Bake for 22–28 minutes, until the edges are golden and the coconut on top is toasted with light brown tips.
Cool completely: Let the bars cool in the pan on a rack for at least 2 hours.
Lift out using the parchment and slice into squares with a sharp knife.