List of textures by atlases made by Unity sprite packer.

SpritePackerIndex.cs

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

namespace IOGames.Utils
{
    
    public class SpritePackerIndex : MonoBehaviour
    {
        [MenuItem("IO Games/Sprite Packer Index")]
        // Use this for initialization
        public static void run()
        {
            var sprites = AssetDatabase.FindAssets("t:Sprite");

            var result = new Dictionary<string, List<string>>();

            foreach (var sprite in sprites)
            {
                var path = AssetDatabase.GUIDToAssetPath(sprite);

                var ti = AssetImporter.GetAtPath(path) as TextureImporter;

                var tag = ti.spritePackingTag;
                if (!string.IsNullOrEmpty(tag))
                {
                    if (!result.ContainsKey(tag))
                    {
                        result.Add(tag, new List<string>());
                    }
                    result[tag].Add(path);
                }
            }

            foreach (var item in result)
            {
                Debug.LogFormat("=====================\nTag: {0}", item.Key);

                foreach (var path in item.Value)
                {
                    Debug.LogFormat("--- {0}", AssetDatabase.LoadAssetAtPath<Object>(path));
                }
            }
        }

    }
}