magento-test/app/code/Magento/SalesRule/etc/sales.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Sales:etc/sales.xsd">
    <section name="quote">
        <group name="totals">
            <item name="discount" instance="Magento\SalesRule\Model\Quote\Discount" sort_order="300"/>
            <item name="shipping_discount" instance="Magento\SalesRule\Model\Quote\Address\Total\ShippingDiscount" sort_order="400"/>
        </group>
    </section>
</config>