WordPress + ACF: Keep the last edited tab selection when post refreshes

Acf_Current_Tab.php

<?php

// Drop this into your functions.php

/**
 * ACF: Keep the last edited tab selection when post refreshes.
 *
 * When a post containing ACF tabs is opened for edits, the currently selected tab
 * will be saved in a transient. Upon save or refresh of the page, the last selected
 * tab will be selected again, making it more convenient to work with ACF tabs.
 *
 * @link https://gist.github.com/gchtr/2d371918f3778683c61f629dbc545972 
 */
class Acf_Current_Tab {
	/**
	 * Name under which the transient for the current tab will be saved.
	 * @var string
	 */
	private $_transient_name = 'acf_current_tab';

	/**
	 * Number of minutes the transient will be saved.
	 * @var int
	 */
	private $_transient_minutes = 5;

	public function __construct() {
		add_action( 'acf/input/admin_footer', array( $this, 'handle_tab' ) );
		add_action( 'wp_ajax_acf_save_current_tab', array( $this, 'ajax_acf_save_current_tab' ) );
	}

	/**
	 * Select tab that was selected in last edit session of the post.
	 *
	 * - If the time the same post that was last edited lies within the time the
	 *   transient exists, the last selected tab will be selected via JavaScript.
	 * - If a new post is opened for editing, the current tab will be overwritten.
	 */
	public function handle_tab() {
		// Run only when post_id is present
		if ( ! isset( $_GET['post'] ) || ! is_numeric( $_GET['post'] ) ) {
			return;
		}

		$post_id = sanitize_key( $_GET['post'] );

		// Check for existing transient
		$current_tab = get_transient( $this->_transient_name );

		// Use value only once, delete transient right away
		delete_transient( $this->_transient_name );

		// The first tab is selected by default
		$tab_index = 0;

		// Get tab index for current post
		if ( $current_tab['post_id'] === $post_id ) {
			$tab_index = $current_tab['tab_index'];
		}

		?>
		<script type="text/javascript">
			(function($) {
				/**
				 * Global to save the current index of selected tab
				 * @type int
				 */
				window.acf_current_tab_index = null;

				acf.add_action('ready', function( $el ){
					var tabIndex = <?php echo $tab_index; ?>

					// Get tab element by index
					var $li = $('.acf-tab-group').find('li:eq(<?php echo $tab_index; ?>)');

					// Select tab only when it’s not the first tab, which is selected by default
					if (0 !== tabIndex) {
						$li.find('a').click();
					}

					window.acf_current_tab_index = tabIndex;
				});

				acf.add_action('refresh', function($tabGroup) {
					var $currentTab;
					var currentTabIndex = window.acf_current_tab_index;
					var newTabIndex;

					// Bail out if we have no jQuery object
					if (false === $tabGroup instanceof jQuery) {
						return;
					}

					$currentTab = $tabGroup.find('li.active');

					// Bail out if no active tab was found
					if ($currentTab.length === 0) {
						return;
					}

					// Get index of active tab
					newTabIndex = $currentTab.index();

					// Bail out if index is initial or previously selected tab is the same
					if (null === currentTabIndex || newTabIndex === currentTabIndex) {
						return;
					}

					window.acf_current_tab_index = newTabIndex;

					// Send tabIndex to backend to save transient
					$.ajax(ajaxurl, {
				        method: 'post',
				        data: {
							action: 'acf_save_current_tab',
							tab_index: newTabIndex,
							post_id: <?php echo $post_id; ?>
				        }
			        });
				});
			})(jQuery);
		</script>
		<?php
	}

	public function ajax_acf_save_current_tab() {
		if ( ! isset( $_POST['tab_index'] ) || ! is_numeric( $_POST['tab_index'] ) ) {
			return;
		}

		$tab_index = $_POST['tab_index'];
		$post_id = $_POST['post_id'];

		$transient_value = array(
			'tab_index' => $tab_index,
			'post_id' => $post_id,
		);

		$result = set_transient( $this->_transient_name, $transient_value, $this->_transient_minutes * 60 );

		if ( $result ) {
			wp_send_json_success();
		}

		wp_die();
	}
}

if ( is_admin() ) {
	new Acf_Current_Tab();
}

It doesn't work if current edit page has more than 1 tab. How should I do it?

Works perfect here: editing page with 3 tabs (and sub-tabs). Thanks!
Note that one could also use localStorage, for a javascript-only solution.