I did it at the JPN office in Setia Tropika, Johor Baru in 2011.

Because the demand has been little, the receptionist did not know which counter I should go to, and directed me to a wrong counter where the staff did the wrong thing.  I had to approach the public relations department, and went up and down in the building several times.  I was told to go to JPJ, but I said I prefer JPN.  Fortunately, the JPN public relations staff knew this service, and finally arranged for me to approach a general-purpose JPN counter, which did it for me at the closing time without a queue number.  If I am not wrong, we are supposed to treat it as a normal MyKad application/renewal request, probably no form to fill up, get a queue number, go to the counter, tell the staff what you want, pay the fee, and wait a few minutes for the driving license to be renewed and loaded into MyKad.

If you like, you can try suggesting to JPN to show this procedure clearly at every office.  From my experience, the JPN director general is pretty accommodating.  She should be able to take appropriate actions, since the suggestion is pretty reasonable.  Just that she can be a bit overloaded with other work.  I try to avoid making the suggestion myself, because of a potential conflict of interest on my part.

JPN contact details :

Bloody hell.. that day I drive without my license but only carry my MyKad. I was stopped by a police for a traffic offence. When asked for my license, I gave them my MyKad but they don't accept. Instead, they give me an additional summon (RM60) for not able to produce my license.

Use mykad as TnG, register at where?