There's a spectrum.
At one end, we have questions already about layout -- things like separating chunks within a chapter, formatting poetry in running text, whether to show the screen shots before or after the corresponding documentation, and so on. Clearly, then, the presentation of writing is on-topic. Questions about using pop-up callouts or linking versus embedding referenced material or formatting for a phone are also on-topic.
There's a lot of space in between and we haven't had a lot of questions in this space, so if uncertain, I suggest trying. Having actual examples to use to determine this part of our scope, rather than just hypothetical questions, should be a big help. I'll apologize in advance if some of them get closed as off-topic, but we'll help you migrate those to other sites if possible so you still get answers.
1 We do allow tools questions, though not the really basic ones like "how do I make things bold in Word?". But questions that are purely about making graphics are not really writing questions, even if those graphics are being used in your writing.