Hello,
Thanks for contacting us.
Et-core-plugin could not be renamed because it will break the structure and settings which are working in couple with XStore theme.
1/ Why do you need to hide it from your client?
2/ Do you know about users permissions? If not, then you are able to provide access to your client with not allowed permissions to see your plugins/themes/posts etc. Read more here -> https://www.wpbeginner.com/beginners-guide/wordpress-user-roles-and-permissions/
3/ Also, you can install XStore White Label Branding plugin from XStore Control Panel -> Plugins. Read more here -> https://www.8theme.com/documentation/docs/white-label-branding-plugin/
Regards















