This is actually one of TaskPaper's most and intended features! Much harder for me to maintain the internal runtime model with the current behavior then outline constrained editing. The idea is that for many users traditional outlining feels restrictive. People are used to edition "plain" text 99% of the time, so structured outline behavior can create frustration.
With that said I do eventually want a separate "outline" model, though not sure when I will get to it. In the meantime I have implemented outline "move" behavior internally, and you can access it through scripts. (And then map keyboard shortcuts to those scripts) More discussion can be found: