I do this too using my remarkable (reader tablet )and then scripts that export highlights / notes which I then index for as plaintext - it makes this process much more seamless.
This way I can go through my annotations sequentially, save highlights / their main ideas, and reformulate my notes into plaintext a bit more clearly.
Where did you hear that?
Edit: Looks like your link to the sibling comment is for extracting annotations from pdf. Are most of the books you're reading on remarkable in pdf format instead of epub?