Perform a change on ALL of your scenes - BE CAREFUL!

PerformChangeOnAllScenes.cs

using UnityEngine;
using UnityEditor.Callbacks;
using UnityEditor;
using UnityEditor.SceneManagement;

// @kurtdekker - 8:01 AM 12/29/2022

public class PerformChangeOnAllScenes
{
	[MenuItem( itemName: "Assets/Perform Change On ALL Scenes")]
	public static void DoSomethingToAllScenes()
	{
		if (!EditorUtility.DisplayDialog(
			"WARNING!",
			"Doing something severe to ALL scenes!\n\n" +
			"BACK UP OR USE SOURCE CONTROL BEFORE RUNNING THIS!!!\n\n" +
			"This could destroy everything you have ever worked for. Are you sure you want to do it?",
			ok: "DO THE THING!",
			cancel: "NOPE!"))
		{
			return;
		}

		// - find all scenes
		string[] sceneGUIDs = AssetDatabase.FindAssets( "t:scene");
		int numScenes = sceneGUIDs.Length;

		Debug.Log( System.String.Format( "We found {0} scenes in total.", numScenes));

		if (!EditorUtility.DisplayDialog(
			"FINAL WARNING!",
			System.String.Format( "We found {0} scenes. Here we go...", numScenes) + "\n\n" +
			"BACK UP OR USE SOURCE CONTROL BEFORE RUNNING THIS!!!\n\n" +
			"This is your LAST CHANCE TO STOP!",
			ok: "DO THE THING!",
			cancel: "NOPE!"))
		{
			return;
		}

		int scenesConsidered = 0;
		int scenesProcessed = 0;
		int errorCount = 0;

		// - iterate and open each Scene
		for (int i = 0; i < numScenes; i++)
		{
			scenesConsidered++;

			var sceneName = AssetDatabase.GUIDToAssetPath( sceneGUIDs[i]);

			Debug.Log( System.String.Format( "Working on sceneName '{0}'...", sceneName));

			var scene = EditorSceneManager.OpenScene( sceneName);

			bool SuccessfullyChangedThisScene = false;

			// TODO: decide if this scene should or should not be processed here!
			if (true)
			{
				SuccessfullyChangedThisScene = true;

				// TODO: put your change-something-in-this-scene code here!

				// TODO: if you have some sort of an error...
				if (false)
				{
					errorCount++;

					SuccessfullyChangedThisScene = false;

					Debug.LogError( System.String.Format( "We had a problem with scene {0}!!", sceneName));
				}
			}

			if (SuccessfullyChangedThisScene)
			{
				scenesProcessed++;

				EditorSceneManager.MarkSceneDirty(scene);

				// - resave the scene
				EditorSceneManager.SaveScene(scene);

				EditorSceneManager.NewScene(NewSceneSetup.EmptyScene);
			}
			else
			{
				errorCount++;
			}
		}

		{
			string s = "FINAL REPORT ON CHANGING ALL SCENES:\n";
			s += System.String.Format( "Considered {0} scenes.\n", scenesConsidered);
			s += System.String.Format( "Processed {0} scenes successfully.\n", scenesProcessed);
			if (errorCount > 0)
			{
				s += "<b><color=#ff8080>";		// red
			}
			else
			{
				s += "<b><color=#80ff80>";		// green
			}
			s += System.String.Format( "Unable to change {0} scenes.</color></b>\n", errorCount);
			Debug.Log( s);
		}
	}
}