Hello Mohammad,
If you need to merge several imported dense clouds in the same chunk, the following procedure is suggested:
- create a new chunk in the Workspace and make it active,
- import dense cloud via File Menu -> Import -> Import Points option,
- uncheck "Set as default" option in the dense cloud context menu in the Workspace pane (right-click on the dense cloud label),
- repeat import and unchecking set as default option for every cloud that you have to import,
- select all the dense clouds in the chunk contents in the Workspace pane, right-click on selection and choose Merge options.
I also suggest to do it in version 1.5.0 (pre-release build has been recently updated) as it should work better for imported clouds and would also allow to use Reset Region for the imported dense clouds, while there are no aligned cameras, if you need to build mesh or DEM surface from it.