Take a screen shot on a Unity Device Simulator window.

TakeScreenShotPlugin.cs

using System;
using System.IO;
using System.Linq;
using System.Reflection;
using UnityEditor;
using UnityEditor.DeviceSimulation;
using UnityEngine;
using UnityEngine.UIElements;

public class TakeScreenShotPlugin : DeviceSimulatorPlugin
{
    public override string title => "Screen Shot";

    Button takeScreenShotButton;

    public override VisualElement OnCreateUI()
    {
        var root = new VisualElement();

        takeScreenShotButton = new Button { text = "Take Screen Shot" };
        takeScreenShotButton.clicked += () =>
        {
            var simulatorWindowType = AppDomain
                                        .CurrentDomain
                                        .GetAssemblies()
                                        .SelectMany(asm => asm.GetTypes())
                                        .Single(x => x.FullName == "UnityEditor.DeviceSimulation.SimulatorWindow");

            // UnityEditor.DeviceSimulation.SimulatorWindow
            var simulatorWindow = typeof(EditorWindow)
                                .GetMethod(nameof(EditorWindow.GetWindow), 1, new Type[0])
                                .MakeGenericMethod(simulatorWindowType)
                                .Invoke(null, new object[0]);

            // UnityEditor.DeviceSimulation.DeviceSimulatorMain
            var simulatorMain = simulatorWindow
                                .GetType()
                                .GetField("m_Main", BindingFlags.NonPublic | BindingFlags.Instance)
                                .GetValue(simulatorWindow);

            // UnityEditor.DeviceSimulation.DeviceInfoAsset
            var currentDeviceAsset = simulatorMain
                                    .GetType()
                                    .GetProperty("currentDevice")
                                    .GetValue(simulatorMain);

            // UnityEditor.DeviceSimulation.DeviceInfo
            var currentDeviceInfo = currentDeviceAsset
                                        .GetType()
                                        .GetField("deviceInfo")
                                        .GetValue(currentDeviceAsset);

            var friendlyName = (string)currentDeviceInfo
                                            .GetType()
                                            .GetField("friendlyName")
                                            .GetValue(currentDeviceInfo);

            var dir = new DirectoryInfo("ScreenShots");
            if (!dir.Exists) dir.Create();

            var path = Path.Combine(dir.FullName, $"{friendlyName}.png");
            ScreenCapture.CaptureScreenshot(path);
            Debug.Log($"A screen shot was saved to {path}");
        };

        root.Add(takeScreenShotButton);

        return root;
    }
}