I noted that you are not allowed to have simultaneous route guidance on the vehicle's own navigation system and on the navigation apps running under CarPlay.

You could have had, for example, route guidance showing up on virtual cockpit based on the vehicle's own navigation system, and route guidance running on Waze, and showing up on Columbus.

The current setup is that you can only have one, or the other.  When you start one of them, it ends the other.

I suppose this is a safety measure, to avoid driver confusion - especially in a scenario in which you are using the voice guided nav. 

What do you think? Would it actually be useful to have two route guidance navs running simultaneously ?   

 

Being an avid caravanner we have used a Garmin Camper which is route specific for a prescribed unit (size, weight etc) however cannot use it now as it requires a 12v supply and when connected to the USB-C port it immediately drops into Computer mode in the belief that it is connected to a computer.  It would be preferable to use Garmin thus avoiding wifi data usage charges.  Has anyone any idea please?

Sounds like you might need something like this USB to 12V Step-Up Converter

Grateful thanks Dave I'll investigate to see if there is one with mini USB terminal to fit Garmin and give it a try.