Add Meta Box to Woocommerce Product #WooMeta

hooks.php

/*
 * Product Meta Fields
 */
add_action( 'woocommerce_product_options_general_product_data', 'woocommerce_product_custom_fields' );
function woocommerce_product_custom_fields() {
	global $product_object;
	
	echo '<div class="product_custom_field">';
	
	// Custom Product Text Field
	woocommerce_wp_text_input( array(
		'id'          => 'tipologiaAppunto',
		'label'       => __( 'Tipologia appunto:', 'woocommerce' ),
		'placeholder' => '',
		'desc_tip'    => 'true' // <== Not needed as you don't use a description
	) );
	
	echo '</div>';
}

/*
 * Save admin product custom setting field(s) values
 */
add_action( 'woocommerce_admin_process_product_object', 'woocommerce_product_custom_fields_save' );
function woocommerce_product_custom_fields_save( $product ) {
	if ( isset( $_POST['tipologiaAppunto'] ) ) {
		$product->update_meta_data( 'tipologiaAppunto', sanitize_text_field( $_POST['tipologiaAppunto'] ) );
	}
}