You could use Advanced Search to view Tasks filtered by a specific person.
You can save those search as Reports if you want to use it regularly.
You can find more information about using Advanced Search as Reports in the following article: Using Search & Advanced Search in Asana | Product guide • Asana Product Guide
I would recommend you to check out the third-party integration Asana2go created by @lpb that may be able to provide you with a solution about creating a report of activity grouped by creator.
I hope this helps! Let me know if you have any follow-up questions.
Have a great Thursday!