This tool allows Parallax2D nodes to automatically Parallax in the editor. It has greater functionalities that increase the ease of level creation. To use, download it into the addons folder in the Godot file manager. Enable it in project settings. Reload the project twice. Open the editor scene in the scene folder. You can use the buttons in the dock or the actions that are in the project settings. I would recommend customizing the included character sprite and the Character to get full functionality. There are a few export variables that you can customize, but it isn't necessary.
Important
For the best results, make sure that the camera you use is in the center of the default viewport.