SwiftUI - How to show Custom Alert in middle of Screen from a half sized sheet

Question

I am adding an overlay[alert] to very first parent View of the application. I need to show this overlay from a sheet, but this overlay got covered by the sheet.

@main
struct ToastApp: App {
    @State var showAlert: Bool = false
    var body: some Scene {
        WindowGroup {
            ContentView(showAlert: $showAlert)
                .overlay(alignment: .center, content: {
                    if showAlert {
                        VStack {
                            Text("I am alert")
                            Text("I am alert Description")
                        }
                        .frame(width: 270)
                        .background(Color.gray)
                    }
                })
        }
    }
}

struct ContentView: View {
    @State var showSheet: Bool = false
    @Binding var showAlert: Bool
    var body: some View {
        VStack {
            Text("Application Most Parent")
            Button("Show Sheet") {
                showSheet = true
            }
        }
        .sheet(isPresented: $showSheet) {
            Button("Show Toast") {
                showAlert = true
            }
            .presentationDetents([.fraction(0.5)])
        }
    }
}

Requirements: I want to keep the custom alert in middle of screen.

Please help.