trigger offcanvas opening when item added to cart (add to code block and just change the class or ID to match your offcanvas)

code-block.js

(function($){ 
  
  let offCanvas = '.my-offcanvas'; // Change to your offcanvas selector (class or ID)
  
  /* When item is added to cart */	
  $( document.body ).on( 'added_to_cart', function(){
    
    /* Toggle the classes to open the offcanvas */
    $('html,body').addClass('off-canvas-toggled');
    $(offCanvas).addClass('oxy-off-canvas-toggled');
    $('.added_to_cart').remove();
    
  });

})(jQuery);