How to create scrollbar in customized window?

Hello! I want to create a scrollbar with handle in this customized unity window. Help me please. Thanks in advance!

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEditor;
 using System.IO;
 
 public class LocalizedTextEditor : EditorWindow
 {
     public LocalizationData localizationData;
 
     [MenuItem("Window/Localized Text Editor")]
     static void Init()
     {
         EditorWindow.GetWindow(typeof(LocalizedTextEditor)).Show();
     }
 
     private void OnGUI()
     {
         if (localizationData != null)
         {
             SerializedObject serializedObject = new SerializedObject(this);
             SerializedProperty serializedProperty = serializedObject.FindProperty("localizationData");
             EditorGUILayout.PropertyField(serializedProperty, true);
             serializedObject.ApplyModifiedProperties();
 
             if (GUILayout.Button("Save data"))
             {
                 SaveGameData();
             }
         }
 
         if (GUILayout.Button("Load data"))
         {
             LoadGameData();
         }
 
         if (GUILayout.Button("Create new data"))
         {
             CreateNewData();
         }
     }
 
     private void LoadGameData()
     {
         string filePath = EditorUtility.OpenFilePanel("Select localization data file", Application.streamingAssetsPath, "json");
 
         if (!string.IsNullOrEmpty(filePath))
         {
             string dataAsJson = File.ReadAllText(filePath);
 
             localizationData = JsonUtility.FromJson<LocalizationData>(dataAsJson);
         }
     }
 
     private void SaveGameData()
     {
         string filePath = EditorUtility.SaveFilePanel("Save localization data file", Application.streamingAssetsPath, "", "json");
 
         if (!string.IsNullOrEmpty(filePath))
         {
             string dataAsJson = JsonUtility.ToJson(localizationData);
             File.WriteAllText(filePath, dataAsJson);
         }
     }
 
     private void CreateNewData()
     {
         localizationData = new LocalizationData();
     }
 
 }