The first thing I would expect is a visualization of the failure. When you move things around and break stuff, let's say by creating two disconnected solids, t

The first thing I would expect is a visualization of the failure. When you move things around and break stuff, let's say by creating two disconnected solids, then I would expect a preview to show that. Also, one problem with FreeCAD is that you need to open a sketch to modify it but often the model you are modifying is then hidden. So now you have to roughly guess the optimal value, close the sketch and inspect the model and repeat this process until you have something usable. If you need to use clipping planes to see inside the model then enjoy setting those up every iteration.