Effective communication between objects across additively loaded scenes is best handled by decoupling the lookup process from the SceneManager hierarchy. Because the Scene boundary acts as a serialization barrier, you must establish a runtime bridge.

1. Create a static Registry class to act as a central hub for active object references.
2. In your script, utilize the OnEnable callback to add the instance to Registry.
3. Utilize the OnDisable callback to remove the instance, ensuring you prevent memory leaks and null reference exceptions in additive scenarios.
4. When an object in another scene requires access, query Registry for the specific type instead of using expensive global searches.

This pattern provides a performant, type-safe way to manage dependencies without direct scene-to-scene coupling.

Additional Tips

• In Unity 6, if you must search for objects, use FindObjectsByType<T>(FindObjectsSortMode.None) as it is significantly faster than legacy alternatives when the order of results is not required.
• For strictly data-driven logic, consider using a ScriptableObject as a shared asset that your script can access from any scene to avoid the need for a scene-based Registry entirely.