Kindle highlights are a cloud service. You can even browse them on https://read.amazon.com/kp/notebook https://read.amazon.com/kp/notebook of course they are s

Kindle highlights are a cloud service. You can even browse them on https://read.amazon.com/kp/notebook https://read.amazon.com/kp/notebook of course they are stored.... From what I read there might even be a toggle option for "annotation backups" in the devices settings.