I would love to see as many solutions to this as possible: use a picker to select a value say from 2-10 and then draw that number of Rectangles. Trying to keep formatting minimal to make code as clear as possible. I think I need to create a struct or something, or two way binding... nevertheless have reached the end of my trial and error.

Note that I was able to create a Picker that changes an Int value! Yay. But in picture two you will see that changing the value doesn't change the number of Rectangles.

import SwiftUI

struct PickerRectsTry: View {
    @State private var numberOfRectangles = 3
    let numbers = [Int](0...10)

    var body: some View {
        VStack {
            HStack {
                Picker("Number of Rectangles", selection: $numberOfRectangles) {
                    ForEach(0..<numbers.count) { index in
                        Text("\(self.numbers[index])")
                    }
                }
                .frame(width: 50).clipped()

                Text("\(numberOfRectangles)")
                    .foregroundColor(.blue)
            }

            // now how to pass numberOfRectangles - I think I need a struct or something
            HStack {
                ForEach(0..<numberOfRectangles, content: { index in
                    ZStack {
                        Rectangle().foregroundColor(.gray)
                        Text("\(index)")
                    }
                })
            }
        }
    }
}

I guess I don't know how to share an image, hopefully you get the point. https://ibb.co/PQsdg81

Thank you @delawaremathguy. I can see how this works, and it does, so I appreciate that. I mostly understand I was being reduundant withi self.numbers . I somewhat understand why I had to add the explicit id. I less understand why I was using content in the first place. And I absolutely don't understand how the end parenthesis sort of worked in both places and sort of not. (That was my last catch as I implemented your solution in my project.) Is there anything you can tell me or place to direct me so that I can understand? You can see how far off I was assuming I needed to create a struct or something.

(I'm doing my best as homework is keeping track of all these different variations and shortened versions that do the same thing. Like Text("\(self.numbers[index])") to just Text("\(index)").

Next up I will be trying to add color pickers to change the fills in the first and last rectangles. But baby steps. Next I will try to get one of the color RGB variables stepping along this future array.

Here's the complete code that works, thanks again @delawaremathguy. Pick the number of Rectangles created in a Vertical Stack

struct PickerRectsTry: View {
    @State private var numberOfRectangles = 3
    let numbers = [Int](0...10)

    var body: some View {
        VStack {
            HStack {
                Picker("Number of Rectangles", selection: $numberOfRectangles) {
                    ForEach(0..<numbers.count) { index in
                        Text("\(index)")
                    }
                }
                .frame(width: 50).clipped()
            }

            VStack {
                ForEach(0..<numberOfRectangles, id: \.self) { index in
                    ZStack {
                        Rectangle().foregroundColor(.gray)
                        Text("\(index + 1)")
                    }
                }
            }
        }
    }
}