Publisher is the equivalent of InDesign. It was meant for brochures and so on. If you want to write a long technical manual today most people use Word. In that respect we are using less powerful software today than our grandparents.
Note: Adobe bought FrameMaker and continues to sell FrameMaker. But Word has captured the market not because of its technical merit but because of bundling.
I have never written any technical manuals, but I'm surprised that Word is the choice of tool. How does one embed e.g. code easily in the document? I feel there must be a better way to do it, maybe some kind of markdown syntax? Latex?
> How does one embed e.g. code easily in the document?
You don't. For APIs and such, documentation is published online, and you don't need Word for that. Word is used in some industries, where printed manual is needed.
What about the printed manuals? I think they still have some of those not too long ago (e.g. Intel manuals). What was the tool chosen? Very curious to know.
Or, maybe a legacy example -- how were the printed manuals of Microsoft C 6.0 written? That was in the early 90s I think.
Note: Adobe bought FrameMaker and continues to sell FrameMaker. But Word has captured the market not because of its technical merit but because of bundling.