Is there a way to import pre-baked GI Atlas (Lightmap + Shadow Map)?

Hi! I have a lot of questions about Lightmapping process. I have a HUGE map and GIA (Global Illumination Atlas) for that. Baking everything from scratch is pain in neck, so I want to load pre-baked maps (which are size of 370 MB). I saw how one guy have done this with his own GIA Loader (here's the video). The thing is that he has Unity 5, I have Unity 2019.1.5f1.

I've tried to make my own importer with that and that information (seriously, that's the only "useful" information I've found), but I think I didn't get it. There's not too much info to understand how everything works in Unity. I also couldn't find any API Documentation. I mean, I've found one, but there's nothing interesting, for my humble opinion.

So, the code of importer by itself. Don't worry, it's awkward.

Code (CSharp):

1. using UnityEngine;
2. using UnityEditor;
3. using System.Collections;
4. using System.IO;
5. using System.Collections.Generic;
6.  
7. public class GIALoader : EditorWindow
8. {
9.     string path = "";
10.     List<LightmapData> data = new List<LightmapData>();
11.  
12.     [MenuItem("SU/Open GIA Loader")]
13.     private static void Open()
14.     {
15.         EditorWindow.GetWindow(typeof(GIALoader));
16.     }
17.  
18.     private void OnGUI()
19.     {
20.         EditorGUI.LabelField(new Rect(10, 0, position.width - 20, 20), "GIA Folder Path", EditorStyles.boldLabel);
21.         //string path = EditorUtility.OpenFolderPanel("Put the folder here", "", "");
22.         //string[] files = Directory.GetFiles(path);
23.         path = EditorGUI.TextField(new Rect(10, 50, position.width - 20, 20),
24.             "Path to GIA Folder",
25.             path);
26.         if (GUILayout.Button("Generate Lightmap Data"))
27.         {
28.             Debug.Log(path);
29.             DirectoryInfo dir = new DirectoryInfo(path);
30.             FileInfo[] files = dir.GetFiles("*.*");
31.             GenerateLightmapData(files);
32.         }
33.     }
34.  
35.     private void GenerateLightmapData(FileInfo[] files)
36.     {
37.         foreach (FileInfo file in files)
38.         {
39.             LightmapData ld = new LightmapData();
40.             Texture2D texture = AssetDatabase.LoadAssetAtPath<Texture2D>(file.FullName);
41.             ld.lightmapDir = texture;
42.             data.Add(ld);
43.         }
44.  
45.         Debug.Log(data.ToArray());
46.         LightmapSettings.lightmaps = data.ToArray();
47.     }
48. }
49.