When creating a driver account, an ID is automatically generated. It is possible to change this ID from the driver's "Dashboard".
You can replace the ID with whatever you want, a number, a name, and so on.
Go to the driver's "Dashboard" by clicking on the driver's ID from the "Drivers list".
From the dashboard, go to the "My account" menu and change the ID in the External ID field:
For example, here if the ID is changed to "NEWID", this is what will appear in the list of drivers for this driver: