Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Strength
ID_CA_IKSPLINE_TAG_STRENGTHParameter: Type
ID_CA_IKSPLINE_TAG_TYPEParameter: Aim
ID_CA_IKSPLINE_TAG_AIMParameter: Align
ID_CA_IKSPLINE_TAG_ALIGN_TANGENTParameter: Axis
ID_CA_IKSPLINE_TAG_ALIGN_AXISParameter: Spline
ID_CA_IKSPLINE_TAG_SPLINEParameter: End
ID_CA_IKSPLINE_TAG_ENDParameter: Twist
ID_CA_IKSPLINE_TAG_TWIST_TYPEParameter: Angle
ID_CA_IKSPLINE_TAG_TWIST_AXISParameter: Twist
ID_CA_IKSPLINE_TAG_TWIST_CURVEParameter: Add
ID_CA_IKSPLINE_HANDLE_ADDParameter: Create
ID_CA_IKSPLINE_HANDLE_CREATEParameter: Remove
ID_CA_IKSPLINE_HANDLE_REMOVEParameter: Index
ID_CA_IKSPLINE_HANDLE_INDEXParameter: Object
ID_CA_IKSPLINE_HANDLE_LINKParameter: Twist
ID_CA_IKSPLINE_HANDLE_TWISTParameter: Depth
ID_CA_IKSPLINE_HANDLE_LENGTHParameter: Offset
ID_CA_IKSPLINE_HANDLE_OFFSETParameter: Display
ID_CA_IKSPLINE_DISPLAY_MODEParameter: Tangent
ID_CA_IKSPLINE_DISPLAY_TANGENTParameter: Tangent
ID_CA_IKSPLINE_DISPLAY_TANGENT_COL