You probably (hopefully) know about the wonderful Solid Element Operations in ArchiCAD.
But did you know that you can do Solid Element Operations on your Solid Element Operators?
For example, you want to remove a volume from your mesh. The area that you want to remove, however, needs to be contoured as well (ie. you don’t want to have a flat plane in the place that the chunk has been removed). Most elements in ArchiCAD have unchangeably flat bottoms though, so you can’t use them as the operator.
What you can do though, is remove the chunk that you want, and then use a second operator to make the required contours on the base of the first operator. This makes sense, eventually, but can be quite difficult to puzzle out what it is that you need to do to achieve what you want. Try it on a couple of things so that you can get a feel for the way that it works.
Once you’ve mastered this technique, there’s a whole lot more that you can achieve by using the Solid Element Operators to bend ArchiCD to your will.