Problem solved! ...But only, I suspect, due to the lucky coincidence that TR and my joypad are both about the same vintage! (Before the days of [half] decent DX...)
It seems my joypad fakes having 6 buttons by using axes 3 and 4 as buttons 5 and 6. And, luckily, TR recognises the same convention. *Actual* buttons 5 and 6 (from a more modern controller) don't register in the control assignment screen, but inputs from axis "Z" and axis "T" are seen as button pushes instead.
The solution was to make a custom joystick device in the control panel, with 4 axes and 4 buttons. Then TR sees all the buttons, and can assign them as required.
Which only leaves me with the task of coming up with some dollars to register Glidos! 😀
Anyway - I guess that some other programs may use a similar "cheat". I haven't had that much chance to experiment, but can VDMS map DX8 buttons onto axes instead? - so that people with more modern controllers can "push all their buttons"? 😉
Regards,
LotBC