Please update the plugin to the latest v3.6.0. There are a couple of new options that may be useful for you:
1. You can now exclude EAN from the admin “Duplicate” product action. There is a new checkbox – “Admin product duplicate” (in “WooCommerce > Settings > EAN > General”). It’s enabled by default, so you need to disable it.
2. You can now output (on the admin product edit page) if EAN is unique in your shop. This can be enabled with the new “Check if unique” checkbox (in “WooCommerce > Settings > EAN > General > Admin product edit page”). However, please note that if you are going to hide the EAN input field with the PHP snippet we’ve discussed in another thread, then this option will have no effect.
Please give it a try and let me know what you think.