Auto generates LODs for the selected object, and parents the generated LODs into a LOD Group with a single button. The object hierarcy is setup so that external importers will automatically recognize the object as an LOD group (the original object is set as '_LOD0' in the hierarchy).
Simply download the python file (.py) and add it through Blender -> Edit -> Preferences -> Add-ons -> Install from Disk.
Select the 'Object' menu, and press the 'Auto Generate LODs' button at the bottom of the menu