Actions and Filters

1. Hide default size chart link on product template

Code:

/* Size chart hide default templates hook */
add_filter('show_default_template', 'show_default_template_flag');
function show_default_template_flag($true){
  return false;
}

2. Add custom filter to display size chart link on specific location for custom product template

Code:

function add_hook_custom_size_chart_position_change_custom() {
 return 'woocommerce_before_add_to_cart_button';//add different hook here
}
add_filter( 'add_hook_custom_size_chart_position', 'add_hook_custom_size_chart_position_change_custom', 10 );