{"category": "Unity Engine/Editor/Extensions", "keywords": "Unity, Editor, Dynamic, Modify, Menu Item, MenuItemAttribute"} Modify menu items dynamically, no need for MenuItemAttribute.

DynamicMenuItem.cs

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

/// <summary>
/// Modify menu items dynamically, no need for MenuItemAttribute.
/// Some methods are not available in earlier versions of Unity.
/// </summary>
public static class DynamicMenuItem
{
    private const BindingFlags bindingFlags = BindingFlags.NonPublic | BindingFlags.Static;


    public static event Action menuChanged
    {
        // Exeption thrown on using EventInfo.AddEventHandler and EventInfo.RemoveEventHandler:
        // System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
        // ---> System.InvalidOperationException: Cannot add the event handler since no public add method exists for the event.
        add => typeof(Menu).GetEvent("menuChanged", bindingFlags)
            .GetAddMethod(true).Invoke(null, new object[] { value });
        remove => typeof(Menu).GetEvent("menuChanged", bindingFlags)
            .GetRemoveMethod(true).Invoke(null, new object[] { value });
    }


    public static void AddMenuItem(string name, string shortcut, bool @checked, int priority, Action execute, Func<bool> validate)
    {
        typeof(Menu).GetMethod("AddMenuItem", bindingFlags)
            .Invoke(null, new object[] { name, shortcut, @checked, priority, execute, validate });
    }

    public static void RemoveMenuItem(string name)
    {
        typeof(Menu).GetMethod("RemoveMenuItem", bindingFlags)
            .Invoke(null, new object[] { name });
    }

    public static void AddSeparator(string name, int priority)
    {
        if (!name.EndsWith("/"))
        {
            name = name.Insert(name.Length, "/");
        }

        typeof(Menu).GetMethod("AddSeparator", bindingFlags)
            .Invoke(null, new object[] { name, priority });
    }

    public static bool MenuItemExists(string menuPath)
    {
        bool menuItemExists = (bool)typeof(Menu).GetMethod("MenuItemExists", bindingFlags)
            .Invoke(null, new object[] { menuPath });
        return menuItemExists;
    }

    public static string[] ExtractSubmenus(string menuPath)
    {
        string[] submenus = (string[])typeof(Menu).GetMethod("ExtractSubmenus", bindingFlags)
            .Invoke(null, new object[] { menuPath });
        return submenus;
    }

    public static void SetChecked(string menuPath, bool isChecked) => Menu.SetChecked(menuPath, isChecked);

    public static bool GetChecked(string menuPath) => Menu.GetChecked(menuPath);

    public static bool GetEnabled(string menuPath) => Menu.GetEnabled(menuPath);

#if UNITY_2023_3_OR_NEWER
    public static bool GetEnabledWithContext(string menuPath, UnityEngine.Object[] context)
    {
        bool enabledWithContext = (bool)typeof(Menu).GetMethod("GetEnabledWithContext", bindingFlags)
            .Invoke(null, new object[] { menuPath, context });
        return enabledWithContext;
    }
    
    public static void UpdateContextMenu(UnityEngine.Object[] context, int userData)
    {
        typeof(Menu).GetMethod("UpdateContextMenu", bindingFlags)
            .Invoke(null, new object[] { context, userData });
    }

    public static string GetHotkey(string menuPath)
    {
        string hotkey = (string)typeof(Menu).GetMethod("GetHotkey", bindingFlags)
            .Invoke(null, new object[] { menuPath });
        return hotkey;
    } 
#endif

    public static void SetHotkey(string menuPath, string hotkey)
    {
        typeof(Menu).GetMethod("SetHotkey", bindingFlags)
            .Invoke(null, new object[] { menuPath, hotkey });
    }

    public static void GetMenuItemDefaultShortcuts(List<string> itemNames, List<string> outItemDefaultShortcuts)
    {
        typeof(Menu).GetMethod("GetMenuItemDefaultShortcuts", bindingFlags)
            .Invoke(null, new object[] { itemNames, outItemDefaultShortcuts });
    }

    /// <summary>
    /// Will clear all dynamic menus.
    /// </summary>
    public static void RebuildAllMenus()
    {
        typeof(Menu).GetMethod("RebuildAllMenus", bindingFlags)
            .Invoke(null, null);
    }
}