Actually, the same thing can be accomplished with my "Auto Drag & Tag" feature request. I'll explain. In EN's current state, if the user is in the "Tips" notebook and highlights the "Linux" tag, then the note window shows only "Tips:Linux" notes. I think that's much simpler than sub-notebooks because one can simply have a set of universal tags that apply to all notebooks and then hierarchical tags as needed. No need to replicate sub-notebooks. Now, back to my idea. The downside with the tags as opposed to sub-notebooks is in importing. Particularly, bulk importing (where is easy to lose