Yes, I ensure I have something in them otherwise the code would not compile since I am referencing it in the application. I've tried to use the Save option at the top of the screen (under the three dot menu) and the only Tab of the code I added that gets saved is the .h file, not the .cpp file. Each time I use the Editor I have to add a tab for the .cpp file before I can compile the code again.
If I download the code from the three dot menu after adding all of my own code via the tabs, then the code is saved locally will all files in it. However, if I close the browser window or click "GO TO IOT CLOUD" and go back to the Editor, the .cpp file is missing again.