A simple way to show a toast in SwiftUI apps over all other view activity.

SwiftUIAppToaster.swift

// Inspired by Federico Zanetello
// https://www.fivestars.blog/articles/swiftui-windows/

import UIKit
import SwiftUI

struct ToastView: View {
    let message: String
    /// Total duration that the toast will be visible on screen
    let duration: TimeInterval
    /// Duration of the movement in and out
    let animationDuration: TimeInterval
    /// Opacity control
    @State private var isVisible = false
    /// Start position
    @State private var offsetY: CGFloat = 50

    var body: some View {
        VStack {
            Spacer()
            Text(message)
                .padding()
                .background(Color.red.opacity(0.8))
                .foregroundColor(.white)
                .cornerRadius(8)
                .opacity(isVisible ? 1 : 0)
                .offset(y: offsetY)
                .onAppear {
                    withAnimation(.easeInOut(duration: animationDuration)) {
                        offsetY = -50
                        isVisible = true
                    }
                    DispatchQueue.main.asyncAfter(deadline: .now() + (duration - animationDuration)) {
                        withAnimation(.easeInOut(duration: animationDuration)) {
                            offsetY = 50 // Moves back down
                            isVisible = false
                        }
                    }
                }
        }
    }
}

final class Toaster {
    
    static let shared = Toaster()
    
    private var toastWindow: UIWindow?
    
    var activeWindow: UIWindow? {
        UIApplication.shared.connectedScenes
            .compactMap { $0 as? UIWindowScene }
            .flatMap { $0.windows }
            .first { $0.isKeyWindow }
    }
    
    func showToast(message: String, duration: TimeInterval = 2.0) {
        if let window = activeWindow,
           let scene = window.windowScene {
            
            if toastWindow == nil {
                let toastWindow = PassThroughWindow(windowScene: scene)
                toastWindow.windowLevel = .alert + 1
                toastWindow.backgroundColor = UIColor.clear
                self.toastWindow = toastWindow
            }
            
            let toastView = ToastView(message: message,
                                      duration: duration,
                                      animationDuration: 0.3)
            let toastViewController = UIHostingController(rootView: toastView)
            toastViewController.view.backgroundColor = UIColor.clear
            toastWindow?.rootViewController = toastViewController
            toastWindow?.isHidden = false
            
            DispatchQueue.main.asyncAfter(deadline: .now() + duration) {
                self.toastWindow?.isHidden = true
            }
        }
    }
}

class PassThroughWindow: UIWindow {
    override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
        // Get view from superclass.
        guard let hitView = super.hitTest(point, with: event) else { return nil }
        // If the returned view is the `UIHostingController`'s view, ignore.
        return rootViewController?.view == hitView ? nil : hitView
    }
}

A Demo of this code