In addition to the multi-tab functionality already in GoodNotes, it would be very useful to be able to open multiple instances of the same document at the same time. An example use case would be flipping between textbook chapters and tthe problems at the end of the chapter. Currently bookmarking provides a way to make it easier to flip back and forth between sections of a text, but it's clunky and much less convenient, and I often end up using my computer instead.