magento-test/app/code/Magento/Cms/Test/Mftf/ActionGroup/ClickBrowseBtnOnUploadPopupActionGroup.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="ClickBrowseBtnOnUploadPopupActionGroup">
        <annotations>
            <description>Clicks on the Browse button in the 'Insert/edit image' model.</description>
        </annotations>

        <waitForElementVisible selector="{{MediaGallerySection.Browse}}" stepKey="waitForBrowseButton"/>
        <click selector="{{MediaGallerySection.Browse}}" stepKey="clickBrowse"/>
        <waitForPageLoad stepKey="waitForPageLoad1"/>
        <waitForElementVisible selector="{{MediaGallerySection.mediaGalleryModal}}" stepKey="waitForMediaGallery"/>
        <waitForPageLoad stepKey="waitForPageLoad2"/>
    </actionGroup>
</actionGroups>