There are many threads on the subject of a deeper hierarchical structure for notebooks. One of the reasons I signed up for a premium account is because I "hoped" that would give me a deeper hierarchical structure. Unfortunately I was wrong. If enough people keep asking for this feature, the EN management might just reconsider accommodating customer demand. After all, the customer is supposed to be king??? Please don't tell me that the answer is Tags. Sure, tags are useful but they don't fit the way I work. I like to browse down a hierarchy as part of my personal search and creative process.