If you use "Joint tasks" then the tasks will appear on your list and on your collaborator's lists. If you have reassigned the tasks to them instead, then it is not currently possible to see all tasks that you have assigned to people in one list.
Would love to have this feature. Related to viewing assigned tasks it would also be fantastic to be able to export assigned tasks as well, or at least to be able to export the Workspace of Collaborators who have shared with me. This would be great for providing client status reports on completed tasks of all team members.
You need this feature to grab the attention of companies (like ours) who are planning to use Toodledo for collaboration.
In addition, you want to have a company administrator Master Account able to do settings for all collaborators only once as a group (columns, accepting collaborators and sharing tasks), instead of logging in/out and doing a hundred of clicks...