Copy all highlighted text in Preview
Unfortunately exporting highlights in bulk is not implemented in Apple Preview (yet).
What you can do:
- Show all notes and annotations from preview in a list like this (press option+cmd+4). But you'd still need to copy them manually. With this list you just get an overview and can jump directly to them within Preview.
- Try the App Highlights, which provides your desired functionality. I doubt it can read the highlights from preview though. Might still be worth a try to verify if it works for you and if you want to use it for this functionality in the future.