VS agents can put a note in your booking that you want to upgrade, but this is not the same as a proper waitlist, so far as I am aware.

I have never heard of VS having a proper waitlist process: for example, when I recently had a PE ticket LHR-IAD and was attempting to upgrade with miles, I was explicitly told that they could not waitlist. In that case it was a question of getting to the airport early and doing the upgrade there.

So, I would suggest that early arrival at the airport is probably the best approach.

BC