Forge Version: 43.3.2
Domum Ornamentum Version: 1.19-1.0.146-BETA

The vertical panels are not being displayed as a category or in the Paperwalls in the Architect Cutter. I think I was able to craft them once then they disappeared from the list at some point.

"Vertical panels" are not a separate thing, they are just panels. You can place panels vertically against any surface.

I swear that I saw a request from one of my villagers for a vertical variant. Old age is kicking in I guess.

That might've been a paper wall then, or that was from previous versions where Domum did not exist yet, and we had some fixed models in Minecolonise itself.