Hi mdemange,
I had a talk withmy dealer about that - at the moment there is no way to change the aux level and he did not know, if there will be a fix in one of the next SW versions...
As you can change the level when you have the normal radio I think it would be a good idea to have that with the navi too
But whatever BMW techies are thinking about... practical solutions seem to get into their minds only n special days during the year
So let us keep hoping...
mwie