And in 2020 I stil struggle to export my Kindle highlights from sideloaded books (not bought from Amazon). And even if I did, I haven't found a note system that lets me centralize all the notes I gather from web, documents and my Kindle.
Maybe one of you can come up with a piece of service and make me tear up a little.
Have you tried https://readwise.io?
I export my kindle highlights from sideloaded books through an iphone app and send them to import@readwise.io. That's better then downloading and uploading the txt file. Web is also covered. Dunno about your docuemnts though.
Maybe one of you can come up with a piece of service and make me tear up a little.