This appears to work, Epic folder pointing to Steam folder
To do from “C:\Program Files\EpicGames\EliteDangerous” (or any folder where your Epic install is from command prompt:
mklink /D Products "C:\Program Files (x86)\Steam\steamapps\common\Elite Dangerous\Products"
If your steam install is not the default one, you need to find the corresponding “Products” folder path.
You need to delete the Products folder from Epic install first.