I think My Tasks should have an option to show all tasks across all projects that have been assigned to me. And please include in the free version too!
That is actually exactly how My Tasks works now. The definition of what shows up in your My Tasks is “all tasks within the workspace which are assigned to me”.
Can you elaborate on what you’re seeing which is different from this? (Screenshots can be helpful here!)
As Phil notes, My Tasks already has the behavior you’re expecting.
Just make sure you are literally the named Assignee (i.e. not just Project Owner or Collaborator or Parent Task Assignee of a Subtask of interest) in the Tasks of interest.
If you want Subtasks to appear in My Tasks, you need literally to be explicitly the Assignee in each such Subtask. Being assigned to the Parent Task isn’t enough.