Allow shared tasks to sync with an individual users to-do list
When creating a shared task list, any user who has been shared the list should see those tasks in their "regular" to-do list as well. This would keep all tasks consolidated, easily viewable in Outlook, and easily synced with mobile devices... instead of having to keep track of multiple lists.
Microsoft To-Do allows User 1 to create a shared list with User 2. User 1 will see the tasks in their to-do list. User 2 can add tasks to the list which will show up in User 1's to-do list, but not in User 2's to-do list. A "shared" list isn't "shared" if all users don't have the equal access.