It seems Disney shipped three unaccessible widgets with their library:
- ExprMain (a sorta executable entrypoint inside the library)
- animCurve (SeExpr primitive for animation curves, unavailable in the open source edition of the parser, yet available as an UI widget)
- deepWater (SeExpr primitive for deep water spectrums, same as above)

This commit also enables the relevant features in the SIP header.