You can do it in the Library Manager. You can move the selected element from the Embedded Library by selecting the icon with the chair "move selected library item", and then in the pop-up window select the target library on BIMcloud.
move icon remains grayedout for pointcloud GSM file. But we found the solution by taking hint from your approach. When inserting pointcloud it asks for path to create LCF folder. From this path we uploaded the LCF file to BIMcloud and added this new BIMcloud library to project file from Library manager. and share the project file again on cloud, after these steps all users on teamwork can now see the pointcloud.