I'm new to Evernote and have been using it for a couple of months. The reason I came across this post is because I began to think that maybe I could have an "ultimate stack" filled with stacks and notebooks of this year. I have many notebooks that may not be used next year, but would like to save them for memories. This is what I thought I'd be able to do, turns out unfortunately I can't. Why have a cluster of stacks and notebooks that are not being used and get in the way of ones that are used on a constant day to day basis? Sub-stacks would resolve this issue. I plan on using EN for years to come and would hope to get this feature implemented sooner or later.