Hi,

Set the email template name and subject.
In the "Body HTML" field, you can design your email as needed, including the button. To add a button, you can use HTML and Odoo placeholders for dynamic data.
Here's an example of an HTML button in the email template:

html;-

<a t-attf-href="/web?#id={{ object.id }}&amp;view_type=form&amp;model=sale.order"" style="text-align: center;color: #008CBA;background-color: #008CBA;">View Sales Order</a>

by using the above html code you can create a button in email template

Hope it helps