In order to delete a contact, you have to change to the detail view. There click on the trash button
with your mouse. Here the icon is also visible only if you have permission to delete. The system asks you a security question to make sure you really want to delete this contact.
If you are sure you want to delete, confirm by clicking the Delete button. If you decide not to continue with this deletion, you can leave the menu again by clicking on the Cancel button.