I wonder if there is a way to list all the reports under Reports tab of Adobe Analytics so that I can have a holistic picture of all the reports.
Based way will be :
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 ... ) .
Alexis's recommendation of using workspace and expanding dimensions would be the most ideal way to get a comprehensive list of 'reports'.