Hi,
There is still no real solution with the owl library (which we use for the carousel), to have vertical sliding.
I've found some things regarding this here:
stackoverflow.com/questions/25079495/how...-carousel-vertically
However, this requires the items to have a defined and fix height which isn't the case with HikaShop. We don't know the height of the elements and it can even change from one element of the listing to the other on the same page.
However, if you add CSS similar to what is described there, changing the dimensions so that it fit your precise case, you should be able to achieve it with the current system. Since you're a developer, you should be able to do it. But as a default easy to use option, I don't see a solution yet.
I suppose we'll actually remove that "vertical" setting from the carousel settings area since I don't think we'll be able to use it unless we redo the whole carousel system with another carousel library.