Thank you for your input! We will consider this functionality in upcoming releases, if it will be popular.
Everyone, please continue voting for this feature if you consider it important.
This would be a realy useful feature and should not be to complicated to implement.
Meanwhile one could use this command to get a full list of assigned certificates:
sudo plesk db "select d.name,c.name from domains d inner join hosting h on h.dom_id = d.id inner join certificates c on h.certificate_id = c.id"