You could also extract an Excel File from the Admin>Report Suite that helps you have a better understanding of all the custom Reports. But to my knowledge, the best way to do this is by connecting to the API call. I used to use the python library for Adobe API called "Dancing Cactus Library" in order to be able to connect with Python IDLE. But I'm not sure if with all the changes Adobe has made to the API it's still possible to do this.... This way you can extract also all the other native dimensions ( and also custom metrics, calculated metrics, segments ... ) .