Yeah, any reference to the scripts is gone. The rest speaks of creating devices and panels in the Cubase UI and is pretty thorough but doesn’t work properly, thanks to a bug that was documented in these forums and reported to Steinberg in 2013. [?!]
As a workaround, new MIDI devices must be created by copying an existing device TXT file and then modifying it to suit, either manually or in the Cubase UI. Thankfully, script formatting is documented in a text file: script documentation.txt.
As of Cubase 8.5 (on Windows 10) the default store of device files can be found in two locations:
- C:\Users<username>\AppData\Roaming\Steinberg\Cubase 8.5_64\Scripts\Patchnames\inactive
- C:\Program Files\Steinberg\Cubase 8.5\Scripts\Patchnames\inactive
But only the first is referenced by Cubase. Be sure to copy your scripts there or Cubase won’t add them to its pick list.
As much as I hate to date myself, my first synth was a JX-3P. New. Not eBay. 
I wrote the short-lived Orpheus MIDI sequencer for IBM PCs too, so I understand what you’re saying.
I understand your point re old technology but as a software developer and business owner of three decades, I feel Steinberg’s treatment of these legacy features is sloppy. Bugs should be fixed. Documentation should be complete and accurate.
Maybe it’s my increasingly-stubborn age talking, but I don’t know that this technology is ready for pasture yet. Regarding vintage MIDI hardware, the prices of used synths just keep going up on eBay. It’s ridiculous (and frustrating, if you happen to be in the market for, say, a Yamaha CS-80 - and who isn’t?). Some items are doubling in value year on year. For a long time, I attributed this to young DJs snapping up TR-808s and 909s because Deadmaus (or whoever) had one, but now I’ve reconsidered as other, more boutique analog synths have followed suit. Clearly, there’s a market.
Anyways, I got this all working, thanks largely to your assistance. Thank you! And I hope my update helps anybody else following this breadcrumb trail.
All the best!