you can create a primary and a secondary navigation by placing your topics as folders for the two different navigations in two different folders in the root folder. you could name the first "primary navigation" and the other "secondary navigation". Then you use the tree-menu Code twice, with the node number of the two folders.
this works here. Each folder created in one of the navigation folders is automatically a new navigation topic, so hardcoding the node-ids of the folders is no obstacle i think. we will soon have our site online, so that you will see the example.