Update:
I have figured how to use my plugin to create new Catalog-Elements.

When I drag and drop a new item on my plan,
how can I control it without changing the SH3D code?
It will be added as HomePieceOfFurniture,
but I want it to be added e.g. as a selfmade class
*** extends HomePieceOfFurniture.

Also I want to modify its properties window.

How can I access the HomeController and its View
from my plugin workspace?