Restricting the ability to change device id.

In Traccar, when users are authorized to edit the device, they can also change the id number. Is there a setting so that users can only change the device name but not the id number?

No.

Is there a part in the code that I can disable?
Customers want to edit the device name but they should not touch the id number.

I cannot tell you exactly place where it needs to be changed in the code, but of course it's possible to customize the behavior in the code if you want.