In 26.1.1 the Header section does not mention or explain page number option in windows.
Thanks, that was fixed at some point without marking it as done, so I never got the proverbial memo (as were a few others you caught).
Generally though, if you run across an undocumented feature the first thing to try is whether it does anything at all (for example, anything in the “Other” tab of Print Setup). Many descriptions were removed for that reason, as I feel it is less confusing to have undocumented features that don’t work, than it is to have documented features that don’t work. Neither condition is great, but it’s a judgement call.
Nor does it mention options to include notes and the synopsis.
The “Content” section is covered generally, as one is expected to know what these things are by this point (and if not there is a cross-reference to where they are explained). So all it explains here is that ticking boxes will include these things. Any more detailed listing would just be printing that sentence over and over again with a different noun. 
index card options does not include force landscape orientation
That one on the other hand, I don’t know about… I mean the checkbox certainly does something, but it doesn’t produce anything we’d think of as “index cards” you could cut out of the paper.
Intended result...
So I don’t know. I think I’ll leave that undocumented for now.
An here is another issue. I can show line numbers in page view despite what the manual shows.
Ah, thanks! That is something that was always a limitation on the Mac, and I never noticed it wasn’t on Windows.
I hope this image helps narrow it down, included page numbers of manual when looking with Microsoft browser
Okay, these are the two sections I was looking at as well, but I don’t see anywhere in here where it is implied that this command should be found in the contextual menu.
There are some commands unique to the latter, which is what that first list in §8.1.3 is all about. The context menu also has some commands found in the main View menu, so they aren’t documented redundantly, to save space, hence the redirect to the View menu appendix if one isn’t clear on anything that is absent from that list.
Perhaps what is being missed here are the words, “Most of the commands”? It’s not saying all of the View menu commands are in the context menu, but most of them—and notably not the Size to Fit command.
Maybe I’m being thick though and missing something obvious to another reader.
But I may have discovered a new one: