pressing the tab key while working in the editor turns to inside mode. Zooming in o a building will hide the roof. While placing stuff inside, the enter key is a toggle to stack on object, It is a bit tricky, and we know it can be improved, But does make editing inside object a bit more productive. Pressing tab again goes back to normal edit mode.
Hope that helps a bit.
Thanks for the suggestion.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit