Oh you mean blocks that are one eighth of a normal one? I bet it's easily modable, just make a model that looks like a block of stairs and mod it in with appropriate collision boxes!
For the core game though, i'm not so sure, it would be a nice addition, but the world of hearth has a standard voxel size, terrain and structures follow them and only entities and furniture are exceptions, the stairs like thees are more structure than furniture, unless you want more classy stairs like ones you might see on beach houses
I could try and mod it in myself, but it might take some time since i'm not so free of time
I'd probably need some variants for other tile types
But totally possible, the only problem is that placed items still count towards the inventory, so it's gonna get messy