Mac OS Swift UI 三栏布局

import SwiftUI

var leftItems = ["left1", "left2", "left3", "left4"]
var middleItems1 = ["middle1-1", "middle1-2"]
var middleItems2 = ["middle2-1", "middle2-2", "middle3-3"]
var middleItems3 = ["middle4-1", "middle4-2", "middle4-3", "middle4-4"]
struct ContentView: View {
    @State var select: String? = "left1"
    
    var body: some View
    {
        VStack
        {
            NavigationView
            {
                List
                {
                    ForEach((0..