Unity Scene Reference Attribute

SceneRefAttribute.cs

using UnityEngine;

namespace ModularOptions {
	/// <summary>
	/// Uses a CustomPropertyDrawer to draw a string field as a SceneAsset object field.
	/// </summary>
	/// <example><code>
	/// [SceneRef] string mainMenu;
	/// </code></example>
	[System.AttributeUsage(System.AttributeTargets.Field)]
	public sealed class SceneRefAttribute : PropertyAttribute {}
}

SceneRefDrawer.cs

using UnityEngine;
using UnityEditor;

namespace ModularOptions {
	/// <summary>
	/// Shows a string variable field as a SceneAsset object reference field.
	/// Fully supports standard built-in Editor features such as Undo, through the use of SerializedProperties.
	/// </summary>
	[CustomPropertyDrawer(typeof(SceneRefAttribute))]
	public class SceneRefDrawer : PropertyDrawer {

	public override void OnGUI(Rect _rect, SerializedProperty _prop, GUIContent _label){
			if (_prop.propertyType != SerializedPropertyType.String){
				EditorGUI.HelpBox(_rect, "Error: SceneRefAttribute only works on strings", MessageType.Error);
				return;
			}
			var selectedScene = AssetDatabase.LoadAssetAtPath<SceneAsset>(_prop.stringValue);

			_label = EditorGUI.BeginProperty(_rect, _label, _prop);
			EditorGUI.BeginChangeCheck();

			var newScene = EditorGUI.ObjectField(_rect, _label, selectedScene, typeof(SceneAsset), false);

			if (EditorGUI.EndChangeCheck()){
				_prop.stringValue = AssetDatabase.GetAssetPath(newScene);
			}
			EditorGUI.EndProperty();
		}
	}
}

This is a way to avoid the pain of having to select scenes by numbers or strings. Just drag the scene you wanna use to the object reference field, or, of course, use the object picker (circled dot to the right of object fields).

Installation: SceneRefAttribute.cs can be put anywhere in your Assets folder, SceneRefDrawer.cs needs to be placed in a folder named Editor (anywhere in your Assets). Then just use [SceneRef] before any string you use want to use as a scene reference.

Note: Renaming or moving scenes will break references as the SceneAsset is being tracked using its path.