指定フォルダ以下のアセットをAddressableとして登録するエディタ拡張.

EditorWindowAddressableAssetsRegister.cs

using System.Collections.Generic;
using System.IO;
using System.Linq;
using UnityEngine;
using UnityEditor;
using UnityEditor.AddressableAssets.Settings;
using UnityEditor.AddressableAssets.Settings.GroupSchemas;

public class EditorWindowAddressableAssetsRegister : EditorWindow
{

    [SerializeField] List<DefaultAsset> m_directoryList = new List<DefaultAsset>();
    private static EditorWindowAddressableAssetsRegister m_instance = null;
    private static readonly string PATH_ADDRESSABLE_ASSET_SETTINGS = "Assets/AddressableAssetsData/AddressableAssetSettings.asset";

    [MenuItem("Window/Custom/AddressableAssetsRegister")]
    static void Open()
    {
        if (m_instance == null)
        {
            m_instance = CreateInstance<EditorWindowAddressableAssetsRegister>();
        }
        m_instance.ShowUtility();
    }

    private void OnGUI()
    {
        SerializedObject serialized = new SerializedObject(this);
        var p = serialized.FindProperty("m_directoryList");
        EditorGUILayout.PropertyField(p, true);
        if (GUILayout.Button("Run")) { Run(); }
        serialized.ApplyModifiedProperties();
    }
    private void Run()
    {
        var settings = AssetDatabase.LoadAssetAtPath<AddressableAssetSettings>(PATH_ADDRESSABLE_ASSET_SETTINGS);
        var schema = new List<AddressableAssetGroupSchema>() { CreateInstance<BundledAssetGroupSchema>(), CreateInstance<ContentUpdateGroupSchema>() };
        foreach (var d in m_directoryList)
        {
            var group = settings.groups.Find(g => g.name.Equals(d.name));
            if (group == null) { group = settings.CreateGroup(d.name, false, false, false, schema); }
            AddAllAssets(settings, group, Path.Combine(ProjectPath(), AssetDatabase.GetAssetPath(d)));
            Debug.Log(AssetDatabase.GetAssetPath(d));
        }
    }

    private void AddAllAssets(AddressableAssetSettings settings, AddressableAssetGroup group, string path)
    {
        var objs = LoadAssetsInDir(path);
        foreach (var o in objs)
        {
            var e = settings.CreateOrMoveEntry(AssetDatabase.AssetPathToGUID(AssetDatabase.GetAssetPath(o)), group);
            e.SetAddress(o.name);
        }
    }
    /// <summary>
    // ディレクトリの中のアセットをすべてロードする.
    /// </summary>
    /// <returns></returns>
    private static Object[] LoadAssetsInDir(string dirPath, SearchOption searchOption = SearchOption.AllDirectories)
    {
        var list = new List<Object>();
        DirectoryInfo dirInfo = new DirectoryInfo(dirPath);
        dirInfo.GetFiles("*", searchOption)
            .Where(file => !(file.Name.Contains(".meta")))
            .ToList()
            .ForEach((file) =>
            {
                var o = AssetDatabase.LoadAssetAtPath<Object>(Trim2AssetPath(file.FullName));
                if (o) list.Add(o);
            });
        return list.ToArray();
    }
    /// <summary>
    /// フルパスからプロジェクトの相対パスを取得する.
    /// 入力例：C:/Users/Taro/Documents/UnityProject/ProjectName/Assets/Main/moge.jpg
    /// 出力例：Assets/Main/moge.jpg
    /// </summary>
    /// <returns></returns>
    private static string Trim2AssetPath(string fullPath)
    {
        var index = fullPath.IndexOf("Assets");
        return fullPath.Substring(index);
    }
    /// <summary>
    /// プロジェクトのパスを返す.
    /// </summary>
    /// <returns></returns>
    public static string ProjectPath()
    {
        return Directory.GetParent(Application.dataPath).FullName;
    }
}