Ok, to say I was missing something big was actually an understatement with regards to the Global Vector table.
While I was searching, I found a nice reference at
https://www.pagetable.com/?p=193 which has side-by-side comparisons of the TripOS documentation to the AmigaDOS documentation and highlights how similar they are.
I have to admit, despite being a developer and Amiga owner for around 30 years, I had never heard of TripOS or knew of its part in the AmigaOS history until this thread. Even the familiar "Amiga Original File System" is an almost verbatim copy of the TripOS file structure
https://www.pagetable.com/docs/amiga...s.pdf#page=485
Just because I know my curiosity won't let it go, I found a rough disassembly of the dos.library to get an idea what the global vector functions do, so I'll dig though that.
Many thanks all
References: