+xI think you can specify any cruise profile you want for the Alternate leg.
A source of confusion maybe:
on 3.9.1, you can double click (PC) or long hold (iDevice) a normal leg and adjust its altitude and power setting.
You cannot however double-click the dashed line to the alternate. The only way (I find) is to double click said leg in the PLOG. Before looking specifically for it I did not even know of this method, I had always clicked on the magenta line.