Preheat your oven to 350°F (175°C).
Grease your 9x13 inch baking pan with butter or line it with parchment paper.
In a large mixing bowl, combine the all-purpose flour, salt, and old-fashioned oats. Mix well and set aside.
In another bowl, cream the softened butter and brown sugar together until light and fluffy, about 3-5 minutes.
Add the lightly beaten egg and vanilla extract to the butter-sugar mixture, mixing until well combined.
Gradually add the dry mixture to the wet ingredients, stirring until just combined.
Fold in the flaked sweetened coconut, semi-sweet chocolate chips, and butterscotch chips until evenly distributed.
Pour the batter into the prepared baking pan and spread it evenly.
Pour the sweetened condensed milk over the top of the batter, spreading it gently.
Bake for 25-30 minutes, or until the edges are golden brown and the center is set.
Let the bars cool in the pan for 15 minutes, then lift them out using the parchment paper and cool completely before cutting into squares.
