This reminds me of my days programming Lisp. Toward the end of the four years I spent coding Lisp full time, on Symbolics Lisp machines, I got to where I could say, "Hmmmm, I need to do 'X', I'll bet there's a function called 'backward-hacking-smooth-styled-X'" and I was starting to be correct a surprising number of times.
SO: How do you give this knowledge to new folks? Somewhere on the site I saw a treemap (a large rectangle, divided into hundreds of smaller rectangles, in various colors, grouped into larger rectangles...) which was supposed to be... helpful? Prideful (look at what all we've built!)? What I get out of it is a scary nightmare - you'll never find what you want here! There's just too much!
And watching one of the demo videos, where the person is showing how they analyzed and visualized some react code, and dependencies, etc., it was always, "Oh, we want to see it this other way, shazam! we have an awesomely excellent tool that just makes that pop right out! But only if you know the arcane sequence of calls/invisible GUI actions to get to it.
I used the (slightly ridiculous) example of the Lisp function above, to illustrate something. I REALLY REALLY REALLY wish no one had EVER used the phrase, "Intuitive!" about their tool or user interface. There is nothing intuitive about your UI. But! But! But! The Mac! 1984! I had a Mac in 1984, I'm typing on one now (after a decade of wandering in that other wilderness :-) and I'm here to tell you the Mac UI used to be (and still largely is) discoverable.
That's the magic sauce.
It's great that you know the 12,011 functions and tools inside GT. I'm sure you'll come up with some nice trip that takes a user through some tiny percentage of those, and then dumps them out at the end in the middle of a rather large city, where they're now supposed to know where every building is, and what's in those buildings. And speaking from experience, it's wildly frustrating to have a few tools at hand, none of which really help much in some new problem, and no freaking clue how to find relevant stuff, and just wind up grinding through a lot of code in a language you're not really fluent in, and generally giving up on the whole mess and going back to the tools you know.
For one small example: someone wants to do something with a spreadsheet file someone gave them, and can't find anything about "spreadsheet" in the docs... because they don't know to save the spreadsheet in CSV format, and there are tools that work with that.
As someone else mentioned, perhaps having an LLM set up with all the stuff to be a guide might help.
Lisp and Smalltalk aren't written languages, they're oral traditions (yeah yeah yeah, Little Lisper, SICP, but those are just starters, and not for the Lisp dialect you're using anyway). Videos may be a start, but... man, I don't envy your task.
Good luck!