There are several approaches to a dynamic navigation in Filemaker. Over the course of the last few years I developed and improved a solution, reducing and simplifying it as far a possible. A free example file can now be downloaded from our website here:
The solution in a nutshell:
1 navigation table for all navigation elements
1 definition of relationships
1 navigation script
1 set of predefined dynamic objects (portals, etc.)
Have fun exploring!