I want to make a room using the DwRmSm kit pieces, but I want a big hole in the floor (actually going to be a lower trench area) but I can't find any isolated ceiling parts to fill in the pattern on the ceiling without covering over the area I want to be open. I've seen areas like this before ingame, so how do I fill in that big hole in the ceiling?

Click on your statics and search for CeilingOnly, you might find something that way. (That’s how those pieces were named in the Fallout’s)

If that fails, remember that you can use rocks and other objects to cover up the exposed gaps. In Dwemer ruins, pipes do this job wonderfully, or even walls rotated on their side (and then covered with other stuff, so it looks decent). In theory, you can build a room using none of the rooms pieces. That's how Bethesda made the dungeons each look a but different.

Well this particular version is supposed to be in pristine "original condition" so putting rubble in the hole won't work...though building some kind of "Roof machine" or something in the hole should work alright. But there will be quite a few of these rooms (either 16 or 25, depending on how big I want to make this complex in the end) So I'll need to make several of these "roof machine" conglomerations and swap them, rotate them, and so on.

Is there an easy "Group" function that can make a block of items act as a unit by default for longer than the time it takes to accidentally click on an item outside the selected group? I'm gonna be copying this room a LOT, and I'll want to be able to do moves on them fairly efficiently.