FS3DCurve describes a curve Shape feature of 3D Curve type
which instance could be created selecting the
button.
Standard > Feature > Standard > Visualizable > SkmDrwPackage > 2DCurve > 2DGeometry > FSSharedGeometry > FS3DCurve
FSUntrim describes a topological Shape feature of Untrim type,
which instance could be created selecting the
button.
Standard > Feature > Standard > Visualizable > MechanicalModeler > GeometricFeature > MechanicalModelerHide > Body > BasicWireFramePackage > Wireframe > BasicWireFramePackage > Surface > FSUntrim