CSV export is very useful!

It was already available in the clipboard after selecting furniture and choosing Edit / Copy menu item. But even if it's mentioned in the help, many users weren't aware of it and clipboard is still buggy under Linux.

I am not fun of wall painting so far .

The painted walls are the ones that touch the modified room, and only walls that intersect each others are recomputed at their intersection. In the more complicated cases you show, you should split walls with Plan > Split wall menu item. Not sure I'll go further than that now. Hope you can understand...