FocusList.swift

import SwiftUI

@main
struct FocusTestApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
        .commands {
            MessageCommands()
        }
    }
}

struct MessageCommands: Commands {
    private struct MenuContent: View {
        // This _has_ to be added to the `View`, won't work if added to `Commands`!
        @FocusedValue(\.selectedMessage) var selectedMessage

        var body: some View {
            Button("Print") {
                guard let selectedMessage = selectedMessage else { return }
                print("selected: \(selectedMessage)")
            }
            .keyboardShortcut("p")
            .disabled(selectedMessage == nil)
        }
    }

    var body: some Commands {
        CommandMenu("Message") {
            MenuContent()
        }
    }
}

private struct SelectedMessageKey: FocusedValueKey {
    typealias Value = String
}

extension FocusedValues {
    var selectedMessage: String? {
        get { self[SelectedMessageKey.self] }
        set { self[SelectedMessageKey.self] = newValue }
    }
}

struct ContentView: View {
    @State private var selectedMessage: String? = ""

    // There are three key pieces:
    // - Pass `selection:` in the List init
    // - Add `tag` to list items
    // - Add `.focusedValue` to the navigation view
    var body: some View {
        NavigationView {
            List(Array(0..<10).map { $0.description }, id: \.self, selection: $selectedMessage) { message in
                NavigationLink(destination: Text(message)) {
                    Text(message)
                        .tag(message)
                }
            }
            // This doesn't work
             //.focusedValue(\.noteValue, selectedNote!)
        }
        // This does
        .focusedValue(\.selectedMessage, selectedMessage ?? "right side should never get called, I hope")
    }
}