You can continue jumping while sneaking.

I noticed that the ability to jump while sneaking was removed in 1.9. So I messed around with it a bit.
Then I noticed that if you hold the jump key, then while in midair hold the sneak key, you will continue to jump while sneaking.

(I wasn't able to attach a video showing the bug, so I just uploaded it to YouTube.)
https://youtu.be/B2fS9HLBk3Q