Get your taxes done using TurboTax

I'm using Premier desktop version. 

 

It has Form 6781, and Turbo Tax put everything in the right place when I entered it from a K-1.  

 

I'm not sure where you'd enter Section 1256 gains directly in the Q&A flow, but you can go to the "forms" view, find Form 6781, and enter stuff there.

 

See if there's something similar in the Online Version you're using.