Hi Ralf,

MoI is not really set up to do this type of extension work right now. It is theoretically possible, for example Petr has done a couple of custom commands here: http://kyticka.webzdarma.cz/3d/moi/

But I don't really expect to have an official "SDK" type extension mechanism ready for version 1.0. It takes quite a lot of additional work to document and support that type of thing, and the documentation for just the basic use of MoI is not even complete yet.

So it is going to be a while into the future before it will be possible to put in the work to make that type of extensions work very well.

If you need to do walls and windows quickly, I'd recommend using something more specialized for architecture like Revit or Chief Architect, something like that. Since those are focused exclusively on architecture they have a lot of pre-packaged functions for placing walls, windows, and doors as sort of smart encapsulated objects.

- Michael