I am interested to see how this compares to https://highlightsapp.net/ but it looks neat, especially if it starts at a place of integration with other platforms.
Keypoints is similar to Highlights App in that it extracts your PDF highlights into Markdown. That said, there are more differences between those two apps than similarities. I've outlined the major differences at [0].
Most importantly, Keypoints stores each highlight as an individual (Multi)Markdown note, so you can filter/gather them freely and independent of its source context. However, each note is self-contained and keeps its context (i.e. to which PDF / publication it belongs), and selecting a note opens again the exact PDF location containing the original highlight annotation.
Each highlight note can have metadata (like tags, labels or citekeys) that can be clicked to filter by these elements. You can cross-link your notes (incl. link types [1]) and your network of notes gets dynamically visualized (the graph can also be used for navigation).
In addition, Keypoints parses recognized elements from the plaintext notes and exposes them as data model properties via scripting (see an example: [2]). This will allow for fine-grained integrations with other apps.
