I want to customize the email template and add some more columns. For now I found out that the "email/items.phtml" seems to be the right file. In the "sales_email_order_items.xml" are all necessary files. So I tried to override them but the only file I can change is the "email/items/order/default.phtml". This is current progress: 1. create the "sales_email_order_items.xml" in my module 2. override the default.phtml
<referenceBlock name="sales.email.order.renderers">
<block class="Magento\Sales\Block\Order\Email\Items\Order\DefaultOrder" as="default" template="email/items/order/default.phtml"/>
</referenceBlock>
That works for the order items but I can't get to override the table head from "email/items.phtml".