SwiftUI & Mac Catalyst | Adding buttons to trailing navigation bar – Ios swift

I don’t think it is possible to do that because:

 @available(iOS, introduced: 13.0, deprecated: 100000.0, message: "Use toolbar(_:) with navigationBarLeading or navigationBarTrailing placement")
    @available(tvOS, introduced: 13.0, deprecated: 100000.0, message: "Use toolbar(_:) with navigationBarLeading or navigationBarTrailing placement")
    @available(macOS, unavailable)
    @available(watchOS, unavailable)
    public func navigationBarItems<T>(trailing: T) -> some View where T : View

This indicates on macOS the function in not available.

I slightly modified your code (to get it to compile) and saw that where it would be is at the red circle below:

My code is:

struct AppSidebarNavigation: View {
    
    enum NavigationItem {
        case home
    }
    
    @State private var selection: NavigationItem? = .home
    
    var isMac: Bool
    
    init() {
        
#if !targetEnvironment(macCatalyst)
        UITableView.appearance().backgroundColor = UIColor(named: "White")
        UITableViewCell.appearance().selectionStyle = .none
        UITableView.appearance().allowsSelection = false
        isMac = false
#else
        isMac = true
#endif
        
    }
    
    var body: some View {
        NavigationView {

            // Main View
            HomeView()
                .navigationTitle("NavTitle")
                .edgesIgnoringSafeArea(.top)
                .navigationBarHidden(isMac ? false : true)
                .navigationBarBackButtonHidden(isMac ? false : true)
                .navigationBarItems(trailing: NavButtons)
        }
        .accentColor(Color("Black"))
        .navigationViewStyle(.columns)
        
    }
}
var NavButtons: some View {
    HStack {
        Button(action: {}) {
            Image(systemName: "plus")
        }
//        Button(action: {
//            print("No")
//        }) {
//            Image(systemName: "plus")
//                .font(.system(size: 14, weight: .medium)).frame(width: 80)
//        }
    }
}

struct HomeView: View {
    var body: some View {
        Group {
            Text("Home View")
            NavButtons
        }
    }
}

struct HomeView_Previews: PreviewProvider {
    static var previews: some View {
        HomeView()
    }
}

struct NavButton_Previews: PreviewProvider {
    static var previews: some View {
        NavButtons
    }
}
struct ContentView: View {
    var body: some View {
        VStack {
            Image(systemName: "globe")
                .imageScale(.large)
                .foregroundColor(.accentColor)
            Text("Hello, world!")
            AppSidebarNavigation()
        }
        .padding()
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}