I only just now found out of a way to download all kindle highlights and notes. Previously I would open the app on my laptop, open the notes and copy them out one at a time.
this has a browser add on but really the line is the best part
1.Drag the above button to your browser's bookmarks bar.
2.Log in at read.amazon.com.
3.Click on a book title.
4.When the book's page has loaded, click on the "Bookcision" link in your browser's bookmarks bar.
5.An overlay will load with just your highlights.
If you are running Chrome, you'll see an option to download your highlights in various formats. Otherwise, just copy and paste