There isn’t a way currently to see what your “altitude” is, however the current gradient of the road you are on is displayed on the mini map in the top right of the screen and when you are on a climb the new climb display pops up in the middle of the screen.
Even if you could see your in-game altitude, that information is not useful in the context you’re suggesting without also knowing the altitude at the top (as well as any ‘dips’ along the way). And, I think, most of the climbs already have a graphic that shows the distance remaining, don’t they? Does this not provide sufficient information?
You can see the course profile on the Zwiftmap website, including the altitude of each part of each climb, including the dips.
So, yes: it would help to see the current altitude.
I know the HUD shows the distance remaining in the ride. I don’t think it shows the distance to the top of the climb, does it? Anyway, I’m asking here about the altitude, which is independent of the distance remaining to the top.
I wonder if instead of “altitude” what is meant here is “remaining elevation”. We get remaining distance but not remaining elevation in the HUD. Pretty sure I’ve suggested it previously but it’s either not that interesting to the majority of riders or you’re expected to get it elsewhere.
You can see the altitude of each part of each route on the course profiles. The game clearly knows the altitudes you’ve been at, because it works out how much elevation you have climbed in each ride.
Maybe few people are interested in it, (though I don’t know why). But the game definitely knows what (virtual) altitude each rider is at.
As for getting it elsewhere, I don’t see how you could do that. At least not as a live-changing piece of data.