How do I add more furniture markers to things? I'm currently working with a chair that only has one marker; right behind it. how do I fix that to get the typical four around markers? I've looked at the base; it only has the option for one marker.

Open a piece of furniture with the desired markers in NifSkope. Open your item in another instance of NifSkope. Copy the branch labeled BSFurnitureMarker in the first instance and paste it over the same branch in the second instance. You may have to fiddle a bit to get the markers to match your item just so.

I'm a little concerned about a chair having a furniture marker "behind it". As the marker determines which animation is used to sit down, that makes me think the character would pass through the back of the chair, which I'm assuming is there or "behind it" wouldn't mean anything. The only furniture you could enter from all directions is a stool.

Of course, once a furniture marker is added to a mesh, the direction of the seated figure shows a "behind" direction, which may not match the mesh's implied direction.