SUMMARY
Some people wish Okular could save annotations in a separate XML file instead of inside the PDF document, which is a feature which will not come back. But it may be useful to be able to export all annotations, to import them in another document.

USE CASE
1. Write a lecture script and deploy it as PDF to your students
2. Students are annotating the script with their questions
3. Students send back a lot of annotated PDFs
4. Open each PDF, copy all annotations, paste them in your own PDF
5. Be well prepared for your next lesson :)

CURRENT STATE
You have to keep all PDFs of each single student, because each contains a single question. You need to switch tabs frequently.

EXPECTED STATE
You have all questions in one PDF, so you can comfortably go trough them.

RELATED following features should be implemented to make this feature easy to use
Bug: 197726 Show annotation comment text in the annotations side panel
D21364: Indicate annotation type by icon in the annotations side panel
D21376: For highlight annotations, show highlighted text in the annotations side panel
Order annotations by y-position on the page.

ADDITIONAL INFORMATION
I suggested this already in Bug: 394775, because its reporters might have an opinion on this.