Hi Oeales,
For the Subsurface Amount, you can add custom outputs by adding an output node and set its usage to scattering0.
I have not been able to find a shader for Designer that supports SSS, so, unfortunately, I can not see the SSS effect in the 3D view inside Designer. However, it works once I get it into Painter.
Regarding Subsurface Color, I don't know. I have not been needing this so far.
