server-tools/mail_template_attachment_i18n/views/mail_template_view.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2018 Onestein
     License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl). -->

<odoo>
    <record id="mail_template_form" model="ir.ui.view">
        <field name="name">mail.template.form</field>
        <field name="model">mail.template</field>
        <field name="inherit_id" ref="mail.email_template_form"/>
        <field name="arch" type="xml">
            <xpath expr="//field[@name='attachment_ids']" position="after">
                <group>
                    <field name="ir_attachment_language_ids">
                        <tree editable="top">
                            <field name="lang" />
                            <field name="attachment_id" domain="[('type', '=', 'binary')]" />
                        </tree>
                    </field>
                </group>
            </xpath>
        </field>
    </record>
</odoo>