Hi, @jochengerster ,
Sorry, for delayed response,
in the document Port 41474 is typo, it should be 41475. first two mentioned ports, i.e. 23 and 1087 can not be changed
The port 41475 is used by CCS (low level debug application). CCS is mentioned in the user guide. This port can be changed in CCS as below:

Please can you ask the customer what exactly the requirement, or more information why he/she wants to change the port number?
I have also attached the updated user guide, Please find the attached and you can forward to the customer.
Thank you. Kind regards.
-Mehul Patel