I have a workaround for this and it works.
First step: Create the function to get the id of the current category:
function getCurrentCatID(){
global $wp_query;
if(is_category() || is_single()){
$cat_ID = get_query_var('cat');
}
return $cat_ID;
}
Step 2: put dynamic option in parent loop with: {echo:getCurrentCatID}
This way it allows to make the filter without problems showing the subcategories