Hi sorry for the radio silence.
Have you tried script-enabling your third-party plugin as described in this post?
As far as BP libraries are concerned, Sk supports these. Look for example at
UKismetRenderingLibrary. It is derived from
UBlueprintFunctionLibrary and has a number of static member functions decorated with the
UFUNCTION macro. Sk automatically finds those via its UnrealHeaderTool plugin and makes them available for use in Sk. In the IDE, browse to
KismetRenderingLibrary to see examples.