I do see that Vertical Slabs were requested back in early 2024 (per: #226 (comment))
There is literally one mod that does this, and I think (no, I know) DO could do it better.
As well, the ability to stack slabs (as per: https://www.curseforge.com/minecraft/mc-mods/double-slabs)
These, obvs, are limited to vanilla, so all of the fantastic DO slabs are left out.
I would kill to see this functionality in DO (and trim a few mods from my list)

To take it a step further, quarter blocks and quarter corners would be amazeballs
See attached for visual desc: