Easy to use but lacks sublists/cards/tasks

I really enjoyed the looks and how easy to use and simple this app is but it failed me when I learned I could not use it for projects that are more complex and require a greater break down of objectives and tasks into several sub-actions. I cannot create sublists and sub cards basically.
Ex: task > subtask 1 > subtask 1.a or
Project A > Objective 1 > tasks > 1 + 2 + 3...

Filipeaac about Trello: organize anything!, v3.4.4