magento-test/app/code/Magento/MediaGalleryUi/Test/Mftf/ActionGroup/AdminMediaGalleryClickAddSelectedActionGroup.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--
 /**
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
-->

<actionGroups xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:noNamespaceSchemaLocation="urn:magento:mftf:Test/etc/actionGroupSchema.xsd">
    <actionGroup name="AdminMediaGalleryClickAddSelectedActionGroup">
        <waitForElementVisible selector="{{AdminMediaGalleryHeaderButtonsSection.addSelected}}" stepKey="waitForAddSelectedButton"/>
        <click selector="{{AdminMediaGalleryHeaderButtonsSection.addSelected}}" stepKey="ClickAddSelected"/>
        <waitForPageLoad stepKey="waitForImageToBeAdded"/>
        <waitForLoadingMaskToDisappear stepKey="waitForLoadingMaskDisappear"/>
    </actionGroup>
</actionGroups>