ソースコード

using System.Collections.Generic;
using UnityEngine.SceneManagement;

namespace Kogane
{
    public static class KoganeSceneManager
    {
        public static IEnumerable<Scene> GetAllScenes()
        {
            var sceneCount = SceneManager.sceneCount;

            for ( var i = 0; i < sceneCount; i++ )
            {
                yield return SceneManager.GetSceneAt( i );
            }
        }
    }
}

使用例

foreach ( var scene in KoganeSceneManager.GetAllScenes() )
{
    Debug.Log( scene.name );
}