It'd be amazing to have Pop-up Notes. Say you're working on a paper with a dense list of questions that you'd like to answer in the same notebook. It'd be good to be able to create a Popup note (UI wise could just be a circular note icon that expands) in an area that you choose, so when you click on it a popup comes up that lets you write within that new popup.

This would also be cool for marking or writing extra notes that you don't want directly onto a document.