According to this article about the Khan Academy SAT practice, the practice system can use your results from the paper tests if you mark the answers in the online practice exam, assuming you use one of the eight tests on Khan Academy. From what I've seen I don't think there's a way to upload other test data to the practice on Khan Academy. I'll definitely escalate your post and get it on the team's radar for further consideration. I think such a feature would definitely be a huge help.

Thank you for posting -- we always love feedback from the community!