It is very disappointing to see that the question, answers, and comebacks have been recycling since 2011. The only thing that has changed is my age (now 72) and my desire to be able to convert my EN notes to a more economical and usable format for my students and descendants.
Why can't we have both nested notebooks and tags? Is there a technical reason? The ability to organise files into a hierarchy of folders (notebooks) and sub folders (sub notebooks) is a reasonable request, isn't it? Why can't we stack notebooks?