Open the first project,then in the upper right corner of the first project click the minimize botton (-) ,there will be two,click the second one,you then should see the project minimized in sonar then open the new one and minimize it also, you should see both projects at the bottom left of sonars profect window minimized,bring up the first project and copy the track you want to transfer,minimize the first one,maximize the second one and go to the menu bar at the top click Edit-Paste.