Yeah, as stated before TMex's TOOL mod is amazing. He has a video showing how to use it and Kate Emerald has one as well that is also really good. It takes some practice but it gets easier to use. The weird thing is that you use it in Live mode, not build mode. I find it nice to have to remove weird things that get stuck on the edges of lots like baby cribs and christmas decorations and bikes that people leave. You can probably use it to add items to the surrounding world but I don't think you will be able to move/remove items from the existing world. I haven't tried yet, though. I will say that using this mod is NOT easy. It takes a long time and anything you do with it takes forever. I would not reccomend redoing a world with this mod.