Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: File
ART_FILEParameter: Open in AI
ART_OPENParameter: Create Materials
ART_CREATEMATERIALSParameter: \u27F3
ART_RELOADParameter: Height
ART_SCALE_FACTORParameter: Layer Offset
ART_LAYEROFFSETParameter: Path Spread
ART_PATHOFFSETParameter: Extrude Depth
ART_DEPTHParameter: Center XY
ART_RECENTERParameter: Hierarchy
ART_SHOW_HIERARCHYParameter: Center Z
ART_RECENTER_ZParameter: Greedy Fill
ART_GREEDYFILLParameter: Auto Close
ART_AUTOCLOSEParameter: Force PDF
ART_FORCEPDFParameter: Width
ART_STROKESCALEParameter: Depth
ART_STROKEASPECTParameter: Rounding
ART_STROKEROUNDINGParameter: Growth
ART_STROKEGROWTHParameter: Offset
ART_STROKEOFFSETParameter: Intermediate Points
SPLINEOBJECT_INTERPOLATIONParameter: Number
SPLINEOBJECT_SUBParameter: Angle
SPLINEOBJECT_ANGLEParameter: Maximum Length
SPLINEOBJECT_MAXIMUMLENGTH