Maybe "TurboTax does not support doing two different things with a single 1099-R" but it certainly pretends it does.
I answered questions in StepByStep mode, Turbotax had the option "RothConversion + CashOut ", looked good until it turned out it filled the form funny way, so that it showed error at the final analysis, and didn't allow to correct it (nonsense directions, referring to non-existing form lines).
Treating 100% of distribution as cash out worked well. It's taxed same way, anyway.
