AnytimeHoldOn.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using UnityEditor;

namespace Unity.Assets.Editor
{
    public class AnytimeHoldOn
    {
        [MenuItem("Help/Hold on")]
        public static void HoldOn()
        {
            var allPaths = AssetDatabase.GetAllAssetPaths();
            for (var i = 0; i < allPaths.Length; i++)
            {
                EditorUtility.DisplayProgressBar("Hold on", allPaths[i], i / (float)allPaths.Length);
                Thread.Sleep(5);
            }
            EditorUtility.ClearProgressBar();
        }
    }
}