This option will cause the selection of any Lidar points that have non-zero segment ID's to select all points with the same segment ID.
To open this tool, change Lidar Draw Mode to Color Lidar by Segment, then select this button from the Digitizer(Advanced) toolbar. This tool is also available from the right click Digitizer > Advanced Selection Option > LIDAR SEGMENT SELECT - Click to Select All Lidar Points in Segment.
This tool requires Global Mapper Pro.
Change the Draw Mode to Color Lidar by Segment.
Select a Lidar point.
All other Lidar points with the same Segment ID are selected.