Custom Taxonomy

functions.php

<?php 

// This code goes in your theme's functions.php 
function form_caracteristica( $object_id ) { 
 	WCVendors_Pro_Form_helper::select( array(
			'post_id'			=> $object_id,
			'id'				=> 'wcv_custom_product_caracteristicas',
			'class'				=> 'select2',
			'label'				=> __('Caracteristicas', 'wcvendors-pro'),
			'show_option_none'	=> __('Select a caracteristicas', 'wcvendors-pro'),
			'taxonomy'			=>	'caracteristica', 
			'taxonomy_args'		=> array( 
									'hide_empty'	=> 0, 
								), 	
			)
	); 
}

function save_caracteristica( $post_id ){ 
	$term = $_POST[ 'wcv_custom_product_caracteristicas' ]; 
	wp_set_post_terms( $post_id, $term, 'caracteristica' ); 
}

add_action( 'wcv_save_product', 'save_caracteristica' ); 

// Now put the following line in your product-edit.php template override 

<?php form_caracteristica( $object_id ); ?>

WCVendors_Pro_Form_helper should be WCVendors_Pro_Form_Helper (See pro plugin - public/class-wcvendors-pro-form-helper.php)