好消息是你太努力了，太努力了。
ObservedObject属性 Package 器可以为你创建这个Binding，你只需要说$options.refreshRate。
这里有一个测试操场供你尝试：

import SwiftUI

enum RefreshRate {
    case low, medium, high
}

class Options: ObservableObject {
    @Published var refreshRate = RefreshRate.medium
}

struct RefreshRateEditor: View {
    @ObservedObject var options: Options
    
    var body: some View {

                                       // vvvvvvvvvvvvvvvvvvvv

        Picker("Refresh Rate", selection: $options.refreshRate) {

                                       // ^^^^^^^^^^^^^^^^^^^^

            Text("Low").tag(RefreshRate.low)
            Text("Medium").tag(RefreshRate.medium)
            Text("High").tag(RefreshRate.high)
        }
        .pickerStyle(.segmented)
    }
}

struct ContentView: View {
    @StateObject var options = Options()
    
    var body: some View {
        VStack {
            RefreshRateEditor(options: options)
            
            Text("Refresh rate: \(options.refreshRate)" as String)
        }
        .padding()
    }
}

import PlaygroundSupport
PlaygroundPage.current.setLiveView(ContentView())

同样值得注意的是，如果你想创建一个自定义的Binding，你写的代码几乎可以工作，只要把它改为计算属性而不是存储属性即可：

var refreshRate: Binding<RefreshRate> {
    .init(
        get: { self.options.refreshRate },
        set: { self.options.refreshRate = $0 }
    )
}

如果我没理解错的话，您希望在SwiftUI中执行Set a Published value in an ObservableObject from the UI (Picker, etc.)。
有很多方法可以做到这一点，我建议您使用ObservableObject类，并在视图中需要绑定的任何地方（如Picker）直接使用它。
下面的示例代码显示了一种设置代码以执行此操作的方法：

import Foundation
import SwiftUI

// declare your ObservableObject class
class Options: ObservableObject {
    @Published var name = "Mickey"
}

struct ContentView: View {
    @StateObject var optionModel = Options()  // <-- initialise the model
    let selectionSet = ["Mickey", "Mouse", "Goofy", "Donald"]
    @State var showSheet = false

    var body: some View {
        VStack {
            Text(optionModel.name).foregroundColor(.red)
            Picker("names", selection: $optionModel.name) {  // <-- use the model directly as a $binding
                ForEach (selectionSet, id: \.self) { value in
                    Text(value).tag(value)
                }
            }
            Button("Show other view") { showSheet = true }
        }
        .sheet(isPresented: $showSheet) {
            SheetView(optionModel: optionModel) // <-- pass the model to other view, see also @EnvironmentObject
        }
    }
}

struct SheetView: View {
    @ObservedObject var optionModel: Options  // <-- receive the model
      
    var body: some View {
        VStack {
            Text(optionModel.name).foregroundColor(.green) // <-- show updated value
        }
    }
}

如果你真的希望有一个“无用的”中间局部变量，那么使用这个方法：

struct ContentView: View {
     @StateObject var optionModel = Options()  // <-- initialise the model
     let selectionSet = ["Mickey", "Mouse", "Goofy", "Donald"]
     @State var showSheet = false
     
     @State var localVar = ""  // <-- the local var
     
     var body: some View {
         VStack {
             Text(optionModel.name).foregroundColor(.red)
             Picker("names", selection: $localVar) {  // <-- using the localVar
                 ForEach (selectionSet, id: \.self) { value in
                     Text(value).tag(value)
                 }
             }
             .onChange(of: localVar) { newValue in
                 optionModel.name = newValue  // <-- update the model
             }
             Button("Show other view") { showSheet = true }
         }
         .sheet(isPresented: $showSheet) {
             SheetView(optionModel: optionModel) // <-- pass the model to other view, see also @EnvironmentObject
         }
     }
 }