Microsoft is quietly working on an overhaul of the Sticky Notes for Windows 10 app, with a new UI which would bring all your notes together in a single pane, but still allow users to tear off a note to leave by itself on the desktop.
ALumia has discovered this feature in a pre-release version of the app, and posted this animation showing the UI in action.
Microsoft is also working on adding tag support to the sticky notes, which can be added by simply typing a word with a hashtag e.g. #stickynotes.
Both features are unreleased, and it is not known when Microsoft will add them to the mainstream app. In the meantime, you can download the current release of the Sticky Notes app from the Microsoft Store here.