@Mark Do
Getting a user's time/duration in a meeting might work using the session resource type API call. However, our Microsoft Graph API documentation with Microsoft Teams should explain more on this. I have also added the respective "teams" tags to this thread so someone from their team can further assist on this issue if needed.
If you'd like to create a feature request you can do so using our MS Graph User Voice Forum.
Additional Link:
Working with the communications API in Microsoft Graph
If you have any other questions, please let me know.
Thank you again for your time and patience.