Not quite filesystem navigation, but SGI IRIX's Performance CoPilot software had an IrixGL (OpenGL's precursor) UI for monitoring things like memory state, CPU/storage loads, etc.

The PCP is absolutely nowhere _near_ the graphical wizardry of the state of this app, and the overlay of executing code atop a given directory structure is quite beautiful (practicality be damned), but I can see the inspiration.

I do wonder if, on a modern Linux system with SELinix, this model (code accessing a directory) is actually closer to viable? SELinux's contexts/labels for subjects overlaying with the same for objects can, I imagine, be visualized. The normal access patterns would be way too overwhelming, I think - but exceptions/policy violations? :ponder: