I hit the same problem, however it does attempt to explain why it needs each persmission: Download files and read and modify the browser’s download history

I hit the same problem, however it does attempt to explain why it needs each persmission: Download files and read and modify the browser’s download history — Required to export data. Store unlimited amount of client-side data — Required to save sticky note data locally. Access your data for all websites — Required to load sticky notes on any page.