For situations where a new project needs to be combined with Cesium (or the City tool), having a custom section tool would be very useful, because plots are rarely rectangular shaped.
The best way i can think of to do this would be to import a model, a simple site boundary-shaped volume, that will be used as a section. This would be more precise then drawing out a custom shape inside D5. It would be easy to update and easy to sync with the main model, so there are no gaps between the model and Cesium (which can happen currently when cutting out with sections boxes).
Thank you in advance for considering it. 