How to edit and return the cloud left in current view by VisualizerWithEditing or any kind of Visualizer

**Is your feature request related to a problem? Please describe.**
I'm designing a GUI labelling to crop several parts from a PointCloud, and provide some widget allowing user to label each of them and save them along with label info.
But while I call VisualizerWithEditing to crop cloud, it will be saved to a file manually specified by user, and I can not get the file or the cropped cloud if user choose not to save.

**Describe the solution you'd like**
I wish VisualizerWithEditing or other Visualizers could allow cropping without saving to a file and after user quit the window the cloud could be retrieved through a method of visualizer, making the editing acts like a function call

**Describe alternatives you've considered**
or at least allow me to specify the file path to save cropped cloud, so that after the visualizer quits, I can get the saved cloud.

**Additional context**
None