di.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:framework:ObjectManager/etc/config.xsd">
    <preference for="Magento\GroupedProduct\Model\Product\Type\Grouped" type="Magento\GroupedProduct\Model\Product\Type\Grouped\Backend" />
    <type name="Magento\Sales\Block\Adminhtml\Order\Create\Sidebar\AbstractSidebar">
        <plugin name="GroupedProduct" type="Magento\GroupedProduct\Block\Adminhtml\Order\Create\Sidebar" sortOrder="100"/>
    </type>
    <type name="Magento\Catalog\Model\Product\CopyConstructor\Composite">
        <arguments>
            <argument name="constructors" xsi:type="array">
                <item name="grouped" xsi:type="string">Magento\GroupedProduct\Model\Product\CopyConstructor\Grouped</item>
            </argument>
        </arguments>
    </type>
    <type name="Magento\Sales\Model\AdminOrder\Product\Quote\Initializer">
        <plugin name="sales_adminorder_quote_initializer_plugin" type="Magento\GroupedProduct\Model\Sales\AdminOrder\Product\Quote\Plugin\Initializer" sortOrder="100"/>
    </type>
    <virtualType name="Magento\Catalog\Ui\DataProvider\Product\Form\Modifier\Pool">
        <arguments>
            <argument name="modifiers" xsi:type="array">
                <item name="grouped-custom-options" xsi:type="array">
                    <item name="class" xsi:type="string">Magento\GroupedProduct\Ui\DataProvider\Product\Form\Modifier\CustomOptions</item>
                    <item name="sortOrder" xsi:type="number">72</item>
                </item>
                <item name="grouped" xsi:type="array">
                    <item name="class" xsi:type="string">Magento\GroupedProduct\Ui\DataProvider\Product\Form\Modifier\Grouped</item>
                    <item name="sortOrder" xsi:type="number">120</item>
                </item>
                <item name="grouped_stock_data" xsi:type="array">
                    <item name="class" xsi:type="string">Magento\GroupedProduct\Ui\DataProvider\Product\Form\Modifier\StockData</item>
                    <item name="sortOrder" xsi:type="number">121</item>
                </item>
            </argument>
        </arguments>
    </virtualType>
</config>