Custom title from 2 hidden fields

I know the extince of the default title Filter but i am stuck how i can get 2 submitted fields in the title?

there are several ways to achieve this, either change the saved post with the action fired at the end of the mapping process (action #16 in the helper codes, see screenshot #8),

add_action('cf7_2_post_form_submitted_to_formulaire-rtl', 'new_formulaire_rtl_mapped',10,4);
/**
* Function to take further action once form has been submitted and saved as a post.  Note this action is only fired for submission which has been submitted as opposed to saved as drafts.
* @param string $post_id new post ID to which submission was saved.
* @param array $cf7_form_data complete set of data submitted in the form as an array of field-name=>value pairs.
* @param string $cf7form_key unique key to identify your form.
* @param array $submitted_files array of files submitted in the form, if any file fields are present.
*/
function new_formulaire_rtl_mapped($post_id, $cf7_form_data, $cf7form_key, $submitted_files){
  //do something.
}

or using a custom filter on the title field (select the filter option from the dropdown menu in the mapping admin page):

add_filter('cf7_2_post_filter-my-form-title','filter_my_form_title',10,3);
function filter_formulaire_rtl_title($value, $post_id, $form_data){
  //$value is the post field value to return, by default it is empty. If you are filtering a taxonomy you can return either slug/id/array.  in case of ids make sure to cast them integers.(see https://codex.ww.wp.xz.cn/Function_Reference/wp_set_object_terms for more information.)
  //$post_id is the ID of the post to which the form values are being mapped to
  // $form_data is the submitted form data as an array of field-name=>value pairs
  return $value;
}

In both cases the submitted values ($cf7_form_data) from your form fields are passed to the callback function, so you can retrieve the fields you need to create your title.

sure, please note that all these helper codes are available in the admin mapping page itself when you click on the filter/action links.