Preheat the oven to 350°. Using a mixer, beat the butter and sugar on high speed until fluffy, about 3 minutes. Mix in the vanilla.
In a medium bowl, whisk together the flour and 1/4 teaspoon salt, then add to the butter mixture. Mix on low speed just until the dough comes together. Press evenly into a 9-by-13-inch baking dish. Using a fork, prick the dough at 1-inch intervals. Bake until golden, 20 to 22 minutes.
In a medium saucepan, melt the caramels with the cream and remaining 1/4 teaspoon salt over medium heat. Stir in the coconut, then spread over the shortbread.
Using a spoon, drizzle the chocolate on top. Let cool completely before slicing.