With the Mac app that I’m developing (Keypoints, see also here, it’s not available yet), I‘m trying to implement something similar. However, my goals are rather to extract the info from the PDF into a selfstanding plaintext/Markdown note, automatically add the source info/citation, and to auto-link this note with the exact location of the extracted/highlighted text in the PDF. So my approach is similar to this:
As with any other note, the user would then be able to add comments, tags, cross-links to other notes, etc. The app is very much scriptable (see e.g. here), and I hope to interface with other apps such as Obsidian.
Here’s an example of how a PDF highlight annotation extracted into a note would look like:
