UnityEditorのToolBarのVisualElementにアクセスして、PlayButtonを消したり表示したりするコード

HidwPlayButton.cs

using System.Collections;
using System.Collections.Generic;
using UnityEditor;
using UnityEditor.UIElements;
using UnityEngine;
using System;
using System.Reflection;
using UnityEngine.UIElements;

public static class HidwPlayButton
{
    static VisualElement RootVisualElement
    {
        get
        {
            const string toolbarTypeName = "UnityEditor.Toolbar";
            const string instanceFieldName = "get";
            const string visualElementFieldName = "m_Root";

            var toolbarType = typeof(Editor).Assembly.GetType(toolbarTypeName);
            var toolbarInstanceField = toolbarType.GetField(instanceFieldName, BindingFlags.Public | BindingFlags.Static);
            var visualElementInstanceField = toolbarType.GetField(visualElementFieldName, BindingFlags.NonPublic | BindingFlags.Instance);
            var toolbarInstance = toolbarInstanceField.GetValue(null);
            var visualElementInstance = visualElementInstanceField.GetValue(toolbarInstance) as VisualElement;
            return visualElementInstance;
        }
    }

    [MenuItem("Play Mode/Hide")]
    public static void Hide() => RootVisualElement.Q("PlayMode").visible = false;

    [MenuItem("Play Mode/Show")]
    public static void Show() => RootVisualElement.Q("PlayMode").visible = true;

}

メニューのHideを押した結果