Piotr Zalog

It works, thanks a lot!

Thanks for qiuck reply.

OK,

I have done:
0. I’ve created custom field with Advanced Custom fields plugin.
1. File to modify was \wp-content\plugins\woocommerce-products-filter\views\html_types\checkbox.php
2. Code looks like (starts in 204-th line):

//before changes: echo $term['name'];
//after:
if( class_exists('acf') ) {
$woo_cat_number = 'product_cat_'.$term['term_id'];
$woo_brand_number = 'pwb-brand_'.$term['term_id'];
$cat_krotka_nazwa = get_field('krotka_nazwa',$woo_cat_number);
$brand_krotka_nazwa = get_field('krotka_nazwa',$woo_brand_number);
if (($cat_krotka_nazwa=='') and ($brand_krotka_nazwa=='')){
echo $term['name'];
}else{
echo $cat_krotka_nazwa;
echo $brand_krotka_nazwa;
}
}else{
echo $term['name'];
}