Use the code below inside a plugin or a child theme so the changes aren’t lost in any Theme update.
Code example
function remove_wp_mobile_menu_widgets(){
// Unregister the Mobile Menu Widgetized Areas.
unregister_sidebar( ‘mobmlefttop’ );
unregister_sidebar( ‘mobmleftbottom’ );
unregister_sidebar( ‘mobmrighttop’ );
unregister_sidebar( ‘mobmrightbottom’ );
}
add_action( ‘widgets_init’, ‘remove_wp_mobile_menu_widgets’, 11 );