Navigation

Please could someone advise how you normally perform your navigation.  For instance, if I had a nav bar coming out from the left hand side on its own layer I would need to duplicate that layer across all my slides. Essentially copy & pasting multiple times for each slide.  This seems an inefficient way of using my time.  Is there a way to have a consistent nav option through out the course whereby I can change only one layer / slide?  

Should the course become rather large staying on top of the nav bar could become time consuming.

As Navigation is the bread and butter for course design there must be an easier way.