Stacks being a business-level object would be helpful. For example, I have two notebooks that both relate to the same business function but I want to keep the topics very clearly separate. One is a repository for information and the other is for 'meta' information about the system itself. I'd ideally like to stack these together in the business so users see and understand the hierarchy at a glance. Since I can't do that, they have to be named in a redundant manner (i.e., "Project Name Info" and "Project Name Meta"). I guess I could use a "meta" tag, but I'd really prefer to keep them separate.