Add a least a tree with one level down called category, making it look just like the quest log

If there's no tree: Create a default tree
If adding an item: Add it to the latest tree or the selected one.

thegreatpeon says:

One thing that would be cool to add is sub tasks.
Goal: Level Blacksmithing to 150

• Acquire 150 Bronze Bars
• Acquire 50 Course Stone

etc.
Then tie some cool fireworks animation to completion.