I agree with this, but I would say that both options work. I like how it organizes things currently, but if this "child list" could be added it would make my workflow quite organized for little input. Keeping things as simple as possible while maintaining productivity is the goal. Although I would like to see color coding in some fashion as to keep larger data sets clear when observed in a tree with many branches.

Perhaps the hotkey of '0' could be used as it is next to O for creating a new "child list". Great tool as-is though.