Hugo:
If you cannot find the objects you need, creating shoji screens with slabs then converting them to library parts (so they rotate to vertical) should not be hard, in the Help files see: Virtual Building > Parametric Objects >
Graphic Creation of Custom Objects.
Unless I am misunderstanding, the tatami mats could be a slab with a tatami texture applied by creating a new material with a tatami texture map, in the Help files see: Configuration > Attributes >
Materials.
You should add a Signature to your Profile (click the Profile button near the top of this page) with your ArchiCAD version and operating system (see mine for an example) for more accurate help in this forum.
David