ReorderableListをList<T>から作成して表示するサンプル

TestReorderableListWindow.cs

namespace hoge
{
    using UnityEngine;
    using UnityEditor;
    using UnityEditorInternal;
    using System.Collections.Generic;

    public class TestReorderableListWindow : EditorWindow 
    {
        [SerializeField] private List<int> list = new List<int>();
        [SerializeField] private ReorderableList reorderableList;

        [MenuItem("EditorWindow/ListからReorderableListを作成するサンプル")]
        static void Open()
        {
            GetWindow<TestReorderableListWindow>();
        }

        void OnGUI()
        {
            if (this.reorderableList == null)
            {
                this.reorderableList = this.CreateReorderableList();
            }

            // ReorderableListの表示
            this.reorderableList.DoLayoutList();
        }

        /// <summary>
        /// ReorderableListの作成
        /// </summary>
        private ReorderableList CreateReorderableList()
        {
            var reorderableList = new ReorderableList(list, typeof(int));

            // ヘッダーの描画
            reorderableList.drawHeaderCallback = (rect) =>
            {
                EditorGUI.LabelField(rect, "ヘッダー");
            };
            
            // 要素の描画
            reorderableList.drawElementCallback = (rect, index, isActive, isFocused) =>
            {
                reorderableList.list[index] = EditorGUI.IntField(rect, "Element " + index , (int)reorderableList.list[index]);
            };

            return reorderableList;
        }
    }
}