After selecting points with one of the selection tools and running the "Extract to file" option - the extraction will be shown in the main window. To be sure, check the title bar: there should be the name of the software, the project location followed by the extraction name (no extraction name will appear if not in an extraction).
Each extraction is independent from the main project and other extractions. Any modification to an extraction will not necessarily be reflected in the main project. Modifications include classifications and deleting/undeleting points. The main project is only updated if the Menu: File / Set Extraction Back function is selected. Thus, it is possible to make several copies of an extraction and experiment different refining and classification scenarios and then choose the best to set back. There is no undo on a “Set Extraction Back” function, but if an untouched extraction was created, it can be set back to return the point cloud as it was before.
The Menu: File / Extractions… is used to select a specific extraction and open it, rename it, delete it or copy it.