Thanks, @DocMont. I could ask nothing more than that you’re listening. 
As I’ve continued to use the docs, I’ve run across a couple of other topics that were unclear to me, so I’ll pass those along here.
World Composition
In the section on World Composition, I struggled for many hours with trying to add sublevels after I had my persistent level created and showing in the Levels window. I kept trying to reproduce the steps in the documentation and in several online video tutorials (both official and community-made). Nothing seemed to work. I had very carefully made sure the persistent level had no existing sublevels because of the warning the editor gives when first enabling World Composition. I would drop another existing level into the Levels window, or onto the persistent level, but never got it to add as a sublevel.
Finally I learned by accident what I had been missing, and what I think should be added to the docs: Sublevels need to be in the same directory as their parent level, or in a descendant under that directory. As far as I can tell, that’s not mentioned in the docs, and the online tutorials seem to take it for granted that everyone knows this. The warning from the editor is what threw me – I had intentionally put my intended sublevels in different directories because I interpreted the warning as “don’t have anything around that can confuse the initial World Composition setup; instead, set up a single level and then use the Levels window to add the others later, as in the tutorials.”
The effect of dropping a Level onto the current persistent level in the Levels window is not obvious from experimenting in the editor, so it may be worth describing that behavior in the docs as well.
Now that I have figured this out, it all makes perfect sense, of course. 
This fits the old adage that “It’s easier to understand the documentation after you’ve learned the software.”
Origin Rebasing
The topic of origin rebasing is familiar to me from other engines, and I understand the floating point precision issue’s causes and effects, and also why we can’t simply use double-precision floating point to make it all go away. I don’t know how to implement this in Unreal Engine, however. It’s mentioned in the documentation, but seemingly only in passing. That’s sad because Unreal appears to be way ahead of most other engines in this feature – something that is hard to do in many engines but very well-supported in Unreal.
I recognize that documentation is always a work-in-progress and never finished, so I’m not upset that a niche topic like this isn’t covered in detail yet. Please simply count my feedback as one asking for this task to be on the to-do list in the near term.
Unreal World Coordinates
The section defining and comparing coordinate systems (local, world, texture, etc.) is extremely useful and something that would have been very easy to take for granted. The one very small addition I would recommend is to explain the customary use of the Cartesian axes in Unreal, with respect to object directionality and cardinal directions.
It’s fairly obvious that +Z is “up” and -Z is “down”, but please consider defining the conventions for “left”, “right”, “forward”, and “backward”. Also, when making landscapes, which axis is traditionally used as “north”?
The concepts of right-handed and left-handed coordinate systems might be worth mentioning as well, since that can profoundly impact import of 3D models.
As before, thanks for listening. I realize at least some of what I’ve suggested here would be a significant effort, but hopefully there are also some easy wins as well.
Have a great day!
