It's not possible right now to transform without constrained proportions. We do get requests for it, though, from time-to-time, so it's possible that it might make it into the app at some point but I don't have any inside information about when/if that might happen.
I'll share the question with the product team though.
Want to add my voice for free transform as well. To use the corners independently to transform a shape opens up a host of possibilities and makes for a lighter workload.
Thanks for taking the time to post. This is a feature is being seriously considered for a future version of Draw.
Sorry I can't say much more than that right now.