Converts legacy sprite packing tags to a 2D Sprite Atlas

SpritePackingTagToAtlas.cs

using System.Collections.Generic;
using System.IO;
using System.Linq;
using UnityEditor;
using UnityEditor.U2D;
using UnityEngine;

// How to use:
// 1. Select a texture that has a "Packing Tag" set
// 2. Open the context menu in the top-right corner of the inspector
// 3. Click "Convert Packing Tag to Atlas"
// 4. Wait...
// 5. There you go, your atlas was created with the same name as the
//    packing tag and in the same directory as the texture selected
// 6. Edit the new Sprite Atlas configurations if necessary
public class SpritePackingTagToAtlas
{
	[MenuItem("CONTEXT/TextureImporter/Convert Packing Tag to Atlas")]
	private static void TransformPackingTagIntoAtlas(MenuCommand command)
	{
		TextureImporter thisImporter = (TextureImporter) command.context;
		string spritePackingTag = thisImporter.spritePackingTag;
		if (string.IsNullOrEmpty(spritePackingTag))
		{
			Debug.Log($"[{nameof(SpritePackingTagToAtlas)}] No sprite packing tag found, ignoring.");
			return;
		}

		var importedTextures = AssetDatabase.FindAssets("t:Texture2D", new[] { "Assets" })
			.Select(AssetDatabase.GUIDToAssetPath)
			.Select(path => (Path: path, Importer: AssetImporter.GetAtPath(path) as TextureImporter))
			.Where(item => item.Importer && item.Importer.spritePackingTag == spritePackingTag);

		var allObjs = new List<Object>();
		foreach ((string path, TextureImporter importer) in importedTextures)
		{
			Object obj = AssetDatabase.LoadAssetAtPath<Texture>(path);
			allObjs.Add(obj);
			importer.spritePackingTag = "";
			importer.SaveAndReimport();
		}

		var atlas = new SpriteAtlasAsset();
		atlas.Add(allObjs.ToArray());
		string atlasPath = $"{Path.GetDirectoryName(thisImporter.assetPath)}/{spritePackingTag}.spriteatlasv2";
		SpriteAtlasAsset.Save(atlas, atlasPath);
		AssetDatabase.ImportAsset(atlasPath);
		EditorGUIUtility.PingObject(atlas);
	}
}