Файл с кодом для видео-туториала: https://youtu.be/zi3l2etjpFM

ExtensionsRuntime.cs

/**
 * Created by Emerald Powder for video tutorial https://youtu.be/zi3l2etjpFM
 **/

using System.IO;
using System.Linq;
using UnityEditor;
using UnityEngine;

public class TreeBase : MonoBehaviour
{

    // ......

#if UNITY_EDITOR
    [ContextMenu("Position tree")]
    public void PositionTree()
    {
        if (Physics.Raycast(transform.position + Vector3.up * 100, Vector3.down, out var hit, 200,
            LayerMask.GetMask("Ground")))
        {
            // Уберите Undo, если вызываете этот метод из верхнего меню для всех деревьев в цикле
            Undo.RecordObject(transform, "position tree");

            transform.position = hit.point - hit.normal * .1f;

            Vector3 normal = hit.normal;

            Vector3 fwd = Vector3.Cross(normal, Vector3.right).normalized;
            fwd = Quaternion.AngleAxis(Random.Range(0, 360), normal) * fwd;
            transform.rotation = Quaternion.LookRotation(fwd, normal);
        }
    }
#endif
}

public class GameMenu : EditorWindow
{
    // Этот метод не нужен, т.к. такая кнопка уже есть в меню Edit. Спасибо "Гоша Ватюнга", "gffd gfg", Bibyter за указание в комментах
    [MenuItem("Game/Clear player prefs")]
    public static void ClearPlayerPrefs()
    {
        PlayerPrefs.DeleteAll();
    }

    [MenuItem("Game/Take screenshot")]
    public static void TakeScreenshot()
    {
        string path = "Screenshots";

        Directory.CreateDirectory(path);

        int i = 0;
        while (File.Exists(path + "/" + i + ".png")) i++;

        ScreenCapture.CaptureScreenshot(path + "/" + i + ".png");
    }

    [MenuItem("Game/Tools/Pos all trees")]
    public static void PositionAllTrees()
    {
        TreeBase[] trees = Object.FindObjectsOfType<TreeBase>();

        Undo.RecordObjects(trees.Select(t => t.transform).ToArray(), "pos all trees");
        
        foreach (var tree in trees)
        {
            tree.PositionTree();
        }
    }
    
    [MenuItem("Game/Check current scene for Standard material")]
    private static void CheckMaterials()
    {
        bool found = false;
        foreach (MeshRenderer renderer in Object.FindObjectsOfType<MeshRenderer>())
        {
            foreach (Material material in renderer.sharedMaterials)
            {
                if (material.shader.name == "Standard")
                {
                    Debug.LogError(material.shader.name, renderer);
                    found = true;
                }
            }
        }

        if (!found) Debug.Log("Well done, no any Standard materials on current scene!");
    }
}

public class LevelContextMenu
{
    [MenuItem("Assets/Set As Debug")]
    public static void SetAsDebug()
    {
        Level selectedLevel = ((GameObject) Selection.activeObject).GetComponent<Level>();

        Object.FindObjectOfType<GameManager>().DebugLevel = selectedLevel;
    }

    [MenuItem("Assets/Set As Debug", true)]
    public static bool SetAsDebugValidator()
    {
        return Selection.activeObject is GameObject &&
               ((GameObject) Selection.activeObject).GetComponent<Level>() != null;
    }
}


[ExecuteAlways]
public class TrafficLight : MonoBehaviour
{
    public bool IsSwitched;

    private MeshRenderer meshRendererComponent;

    public Material Gray;
    public Material Red;
    public Material Green;

    private float timeToSwitch = 1;

    private void Start()
    {
        meshRendererComponent = GetComponent<MeshRenderer>();
    }

    private void Update()
    {
        if (Application.IsPlaying(gameObject))
        {
            timeToSwitch -= Time.deltaTime;
            if (timeToSwitch < 0)
            {
                IsSwitched = !IsSwitched;
                timeToSwitch = 1;
            }
        }

        meshRendererComponent.sharedMaterials = new[]
        {
            Gray,
            IsSwitched ? Gray : Red,
            Gray,
            IsSwitched ? Green : Gray,
            IsSwitched ? Red : Gray,
            Gray,
            IsSwitched ? Gray : Green
        };
    }
}

[ExecuteAlways]
[SelectionBase]
public class RepeatedObject : MonoBehaviour
{
    public Vector3 Offset = Vector3.forward; 

    [Min(1)] public int Count = 1;

    private void Start()
    {
        if (Application.IsPlaying(this))
        {
            CorrectChildCount();
            Destroy(this);
        }
    }

    private void Update()
    {
        CorrectChildCount();
    }

    private void CorrectChildCount()
    {
        Count = Mathf.Clamp(Count, 1, 1000);
        
        if (transform.childCount < Count)
        {
            for (int i = transform.childCount; i < Count; i++)
            {
                Transform instantiate = Instantiate(transform.GetChild(0), transform);
                instantiate.Translate(Offset * i);
            }
        }
        else if (Count < transform.childCount)
        {
            for (int i = transform.childCount-1; i >= Count; i--)
            {
                DestroyImmediate(transform.GetChild(i).gameObject);
            }
        }
    }
}

[ExecuteAlways]
public class InspectorConstraints : MonoBehaviour
{
    public Color[] Colors = new Color[2];
    
    [Space]
    
    [Min(0)] public int ColorIndex;
    public int EvenNumbersOnly;

    private void Start()
    {
        GetComponent<MeshRenderer>().sharedMaterial.color = Colors[ColorIndex];
    }

    private void Update()
    {
        if (ColorIndex >= Colors.Length) ColorIndex = Colors.Length - 1;
        if (EvenNumbersOnly % 2 != 0) EvenNumbersOnly++;
        
        GetComponent<MeshRenderer>().sharedMaterial.color = Colors[ColorIndex];
    }
}