My documentation is organized around tasks like sending MIDI or syncing databases. A few people lately have asked for documentation that goes through every screen in the app and explains every button. But my experience as a developer is that very few people actually read these kinds of user manuals. And my experience as a user is that they are rarely helpful, because there often isn't anything more to say about a button than what it already says in the interface.
When users ask me for help, they never ask questions like, "What does the Broadcast Screen switch on the Device Linking screen do?" They ask questions like, "Why doesn't my slave device see my master device?" That kind of question requires information gathering and then a personalized explanation, and couldn't be answered by a user manual. The handful of questions that do have the same answer every time are listed in in the FAQ.
So, please be honest. If a manual like this existed, would you have used it when you were learning about the app?
Or can you give examples of buttons and options whose function isn't clear?