Different Approach
Every past-paper question, sorted by topic.
Papers, sorted by topic
Question papers and mark schemes with a contents list, so you can go straight to differentiation rather than hunting through a decade of PDFs.
Write on them
Annotate any question with a pen or a finger, on a tablet or a phone. Your notes are saved as you go and follow you between devices.
Pick up where you stopped
Every document remembers the page you were on. Close the tab mid-question and it is still there tomorrow.