Checkbox shortcode with multiple default values

Hi!

Is it possible to select multiple checkbox values in a shortcode tag?

My current setting:

Shortcode on different pages with different default values:

[contact-form-7 id="xxxxxxx" title="ContactForm1" wpcf7_chkbox_products1="Value3" wpcf7_chkbox_products2="Value2"]

Form with checkboxes:

...
[checkbox wpcf7_chkbox_products1 default:shortcode_attr "Value1" "Value2" "Value3" "Value4"]
[checkbox wpcf7_chkbox_products2 default:shortcode_attr "Value1" "Value2"]
...

functions.php:

add_filter( 'shortcode_atts_wpcf7', 'custom_shortcode_atts_wpcf7_filter', 10, 3 );
function custom_shortcode_atts_wpcf7_filter( $out, $pairs, $atts ) {
  $my_attr = ['wpcf7_chkbox_products1', 'wpcf7_chkbox_products2'];
  foreach ( $my_attr as $key => $value ) {
    if(isset($atts[$value]))
    {
      $out[$value] = $atts[$value];
    }
  }
  return $out;
}

This works properly for one default value to be checked!

But how can I select multiple default values?
Example: wpcf7_chkbox_products1 should have “Value1” and “Value4” selected.

Can anyone of you please help me with this? Thank you in advance!