One question and many answers. Generally the answer is yes. You use a park bench as an example. One way is to just create a vertical plane through the middle of the bench. Then intersect the plane with the model. This cuts the bench in half, then you the erase tool and get rid of half the bench. Of course that leaves one side of the bench unsupported. So you take the remaining bench end and duplicate the end piece. If the end piece does not have left/right symmetry, you copy the end piece and scale the end piece to -1. Now you have a flipped bench end to attach to the unsupported end of the bench. Instead of erasing you can also select half and delete the selected half. Su8 also has dynamic components. I have not used them much, but the idea is you can make a component called bench and give it a length attribute. Then you can look at the components attributes and if length is one of them, you can reset length to any value you want. Lets say you built a car engine and the air filter was a component. You just select the air filter and then delete the instance of air filter from your model. There are also layers. A layer could be something like all glass windows in a house. You delete the entire widows layer and all window are gone in a key stroke. Yes, you can erase anything.