A solution to this would be really cool, i'm running the same case, i need to copy and paste every events from the first level to every other levels when i do a change. I've writted everything so i have no modification to make when copy/paste to any level. I always set an active object to global before to edit its frames so it's edited in every scenes. But it's not the best way to make a game...
I've also made a level editor, but in my case on ANDROID only, a level loaded from my level editor (using add backdrop as obstacle or add backdrop) uses more resources than a built-in level, so i prefer to copy/paste every events for better performances.