in order to customize it you have to go to the plugin file in your server host and you will see a file called EnderDragonEggPowersPlugin you will see a config file and you can customize it in the config file, make sure to save the changes.
This egg is perfect for smp with no plugin, this eggs gives the holder potion effects when they hold the egg, the effects can be removed if the egg leave the inventory, the effects can be customized in the config file