This may be user error, but it seems like when you use branching, all questions after the branching question are hidden until you answer the branching question. It would be better if the full survey was visible, except for any drill-down question, which would just show up in the list based on the response to the branching question.
I don't personally think this is a good idea, or if it is it should be an optional setting. There may be questions you don't want people who make some answers to see. Or maybe I misunderstood your idea.
Office 365 Japan Support Team also filed the same issue.
"I hope for a change in Microsoft Forms branching settings"
I'm having the same issue