The help file states the following for snow load analysis:
Limitation

Currently, AutoPIPE only considers snow loading as linear analysis. Load sequencing does not apply to snow loads and such results should not be considered. For analysis sets that consider Gaps/Friction/Soil, the snow loading checkbox should remain unchecked.

And when Snow Load is applied to a non-linear set, it does not show up in Code Combinations. It has to be added manually.