Hi Uwe,
Thanks for reaching out!
While this is not a feature that is available out of the box, we do have a snippet that you can add to your functions.php file in your child theme to accomplish this. To get the slug for the additional field you want to reorder, you can right-click the field in Filter Bar and use the inspector tool (see screenshot). To apply this to multiple fields, you can change
if ( $slug == '_ecp_custom_2' ) {
to
if ( $slug == '_ecp_custom_2' || $slug == '_ecp_custom_3' ) {
and so on to add as many as you need.
Let me know how it goes or if you have any questions!
Thanks,
Jennifer