Apologizing in advance if this is in the wrong category.
There’s a building plugin called BrushTool by XAXA, and it is very useful for building maps. However, I don’t know if it’s safe to use, and I’m fairly certain XAXA has another plugin that is known to deliver the RoSync Loader Virus.
The BrushTool is safe, I actually have it. It can lead to disaster though, if you copy and paste too many things, it can slow down your game. Don’t overuse it!