If I want to add a new template, because I might want to set up a mail template in French, I do this by adding a new line.
I choose department type, sales.
I choose the document type, sales order.
I choose the language code French.
And in document template, I create a new document template for the content of my email template.
And I choose the language code.
Now, a setup line has been made and I can open the template card and fill out the template for my French email template.