How to reverse the bounds parameter of a slider

You cannot "reverse" the bounds.
You will have to use some very basic math to calculate the desired value.

According to the docs, Slider takes a ClosedRange for the "in" parameter,
and a ClosedRange is (https://docs.swift.org/swift-book/LanguageGuide/BasicOperators.html):

"The closed range operator (a...b) defines a range that runs from a to b,
and includes the values a and b.
The value of a must not be greater than b."

Thank you for the reply and the understanding!

Yes, I agree about doing the math.
Originally, I thought I could apply the math in the bounds parameter.
I didn't realize that I could do so in the value parameter.

Thanks to Javier from swiftui-lab.
Here is what he posted:

As far as I know, the Slider requires a range where the lower bound of the range is "lower" than the higher bound. You can work around that problem, if you use an intermediary binding, that converts the value. In the example below, I called it bridge:

Code Block 
struct ExampleView: View {
   @State private var value: Double = 0.5
   let range = 0.3...1.3
   
   var body: some View {
     let bridge = Binding<Double>(get: {
       return range.upperBound - value + range.lowerBound
     }, set: {
       value = range.upperBound - $0 + range.lowerBound
     })
     
     Form {
       Text("Value = \(value)")
       
       Slider(value: bridge, in: range, onEditingChanged: {
         print("\($0)")
       })
     }
   }
}