Spray a 9 x 13-inch baking pan with cooking oil then line it with parchment paper.
Place the graham cracker crumbs and the melted butter in a bowl. Toss with a fork until the crumbs are moist and hold together when squeezed with your hand.
Dump the crumbs in the middle of the pan and then press them into an even layer with your fingers or the back of a flat-bottomed cup.
Spread to edges of the pan with a spatula.
In this order, sprinkle the chocolate chips, butterscotch chips, pecans, and then sweetened coconut over the top of the condensed milk.
Gently press the ingredients down with your palm so they stick to the condensed milk.
Bake until the edges of the bars turn golden-brown and start to pull away slightly from the sides of the pan.
Remove from the oven and sprinkle with the sea salt (if using).
(Stick them in the fridge for a few hours or overnight if needed to help firm up.) Cut into 24 pieces and store in an airtight container with wax paper or parchment paper between layers.
