Using your stand mixer (or you can do this by hand with a wooden spoon in a mixing bowl), combine the melted butter, cake mix, 1/3rd cup condensed milk, , lemon juice, 1 cup chocolate chips, salt, 1 1/2 cups chopped pecans (from above), and 1 cup toasted coconut from above).
Divide the brownie dough in half. Press half the dough into the greased pan, I like to put a little more than half in the pan, but equal is fine. Set aside other half for the topping.
Bake the bottom layer at 350 for 10 minutes.
While baking, put the unwrapped caramels (or caramel nibs) and 1/2 cup condensed milk into a microwave safe bowl and put into the microwave. Microwave in bursts of 30 seconds and mix between bursts until the caramel is melted. Mix in 1 cup of the toasted coconut and the remaining 1/2 cup of toasted pecans.
Remove the baking dish from the oven. If you can allow the brownie layer to cool for about 10 minutes ... the top is a little loose ... and then pour the caramel layer over top of it and smooth it out. It is best to pour the caramel layer near the edges since they are more likely to pull the freshly cooked brownie up, then spread inward (not like my picture below).
Optional, I sometimes add another half cup of milk chocolate chips to the tip layer before spreading it. In the pictures below, I added them by hand after spreading them, but now I just combine them before spreading them and they come out better.
Then crumble (by hand) the second half of the brownie mixture on top of the caramel layer and place the pan in the oven. Bake for 18 - 20 minutes.
Once the pan is cool to the touch, place it in the fridge for at least 30 minutes to allow the caramel to set before cutting into bars. I almost always leave it in the fridge overnight, which makes it easy to cut for a potluck - then once the bars come up to room temperature the caramel is nice and soft.
Prior to cutting, you can drizzle some store bought caramel sauce (like the one for ice cream) over the top for more stickiness.