Beat butter in the bowl of an electric mixer on medium to high speed for 30 seconds. Add sugar and salt; beat until combined, scraping sides of bowl occasionally. Beat in the flour on low speed until combined. Press two-thirds of the crust mixture into the bottom of an ungreased, 13x9x2-inch baking pan; set aside.
Microwave sweetened condensed milk and caramels in a microwave-safe bowl on HIGH 2 1/2 minutes or until melted, stirring after 1 1/2 minutes. Stir in nuts and vanilla. Spread hot mixture over the crust. Dot with remaining crust mixture. Bake 25 to 30 minutes or until crust is golden. Cool in pan on a wire rack. Cool bars thoroughly before cutting.