So I get the following error when I stop play in editor mode.
Some objects were not cleaned up when closing the scene. (Did you spawn new GameObjects from OnDestroy?)
The following scene GameObjects were found:
Save System
it's something I need to do but I cant figure out what
Make sure your Save System has a data serializer (e.g., JsonDataSerializer) and a saved game data storer (e.g., PlayerPrefsSavedGameDataStorer). Otherwise the Save System will create them (unnecessarily, really) to do final cleanup when exiting play mode.
I've added some automatic cleanup in the next update, so you can just ignore the message for now if you want to wait for the update instead.