Hi There,
That is not how footer widgets work on X.
Footer widgets will be added on top footer above bottom footer.
To change the plus symbol from top for the word MENU you can add this code at your child theme’s functions.php since this may not work at customizer’s custom css.
add_action('wp_head', function(){ ?><style>.x-btn-widgetbar .x-icon-plus-circle:before { content: "MENU" !important; } </style> <?php } );
Hope that helps
Joao