post_grid_filter_grid_item_read_more

You can filter grid item read more text as following

function post_grid_filter_grid_item_read_more_extra($read_more){
    
    
    return $read_more.' Hello';			
                    
  }

add_filter('post_grid_filter_grid_item_read_more','post_grid_filter_grid_item_read_more_extra');