But I think you can get around that by designating one more z-level than you need, and then removing that. Blueprint mode or designation priorities might also work.
Tell you what, I am going to try now, will post my results shortly.
Edit: Yes this works. After finishing the designation, it will change to the corresponding stair type. By doing one more z-level, you move the "down/up only" layer there, and can remove it. The designations in the level below will not change as a result.
For anyone wondering: Yes, this is still an improvement over the old way of doing it.
More generally, it speaks to a level of sloppiness that tells me I'm better off waiting a couple of years. I've played a lot of buggy DF builds over the years. It's just part of the experience, but I don't have as much free times as I used to so I'd rather wait than play through the bugs these days.
---v---
---^---
To make a very tall staircase, you can either stack pairs of stairs next to each other (this approach actually has some gameplay benefits, but isn't usually necessary): ---v-----
---^v----
----^v---
-----^---
Or, you can use up/down stairs, which are a single block that acts as both an up and a down stair: ---v---
---x---
---x---
---^---
In the ASCII game, you had to place all of these manually, so you were in full control. In the new Steam game, it's my understanding that you just select the top and bottom layers for your staircase and it automatically builds the "right" stair types for you. The problem I have seen reported is that sometimes it will erroneously designate something like this: ---v---
---v---
---x---
---^---
This staircase does not allow dwarves to transit from layer 2 up to layer 1, and permanently removes material, meaning it's not possible to completely fix the mistake.I did notice that it seems like dwarves won't/can't dig straight up with stairs, they need another path up. Not sure if that's new or pre-existing limitation, as I haven't played classic in over a decade.