Unity Save Play mode
Unlike other tools (such as PlayModePersist), this approximates the common trick of copy/pasting gameobjects from play mode to edit mode.
We couldn't find a way to do this exactly as Unity does, so it serializes and deserializes gameobject hierarchies manually, mostly using UnityEngine.JSONUtility.
It's more of a hammer than a scalpel, but despite its drawbacks it can be a huge time saver so we're releasing it for anyone to use and improve. This tool is experimental. If something goes wrong, backups of your scenes are saved to a Backups folder on your desktop.