Hello
You won`t find any comparable kind of documention available to other 3D software.
It is the Wiki, this Forum and a handful of people who produce video tutorials every now and then.
The rest is up to you and your willingness and eagerness to tackle Terragen.
Search and browse this forum and you will see that you are beating a dead horse so to speak.
There simply seems not to be the manpower behind this software to get up to par with the rest of the 3D world.
That said...
This forum is a gold mine of information - you just have to dig it out.
A lot of the basic and often advanced processes described in older and old forum posts are still true and usable to this day.
Search and you will find. If not, ask and you will get help. There is no question asked unanswered here. Simple as that.
Lots and lots of files in the File sharing section to disect and learn from.
The Wiki holds a lot of information. Even if it is incomplete, very often outdated and more geared to the technical minded.
My first stop is always the Reference section. There are a lot of examples for nodes and settings in form of animated gifs.
Also, there are some good articles on the basics helping to understand the underlying inner workings of Terragen.
It is kind of old fashioned webbrowsing over there, though. Real hyperlink based browsing
This is the -sad but true - bulk of people providing tutorials:
https://planetside.co.uk/terragen-tutorials/at last most of them are free tutorials.
There are - very - few tutorials from bigger players, but not a lot.
So, that`s about it (I`d say).
"I just hope that forum QA isnt the way of learning this software because that is simply absurd."
If that is not the way you want to climb the Terragen ladder then you are out of luck. My personal 2 cents of course.
THAT SAID:
Terragen`s ability to render accurate and beautyful images of the earth, the atmosphere, clouds and the universe is - {42} - outstanding!
And you won`t find any better. This also seems to be the general consensus. You just have to find out how to to it.
CHeers, Klaus