Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: File
ART_FILE
Parameter: Open in AI
ART_OPEN
Parameter: Create Materials
ART_CREATEMATERIALS
Parameter: \u27F3
ART_RELOAD
Parameter: Height
ART_SCALE_FACTOR
Parameter: Layer Offset
ART_LAYEROFFSET
Parameter: Path Spread
ART_PATHOFFSET
Parameter: Extrude Depth
ART_DEPTH
Parameter: Center XY
ART_RECENTER
Parameter: Hierarchy
ART_SHOW_HIERARCHY
Parameter: Center Z
ART_RECENTER_Z
Parameter: Greedy Fill
ART_GREEDYFILL
Parameter: Auto Close
ART_AUTOCLOSE
Parameter: Force PDF
ART_FORCEPDF
Parameter: Width
ART_STROKESCALE
Parameter: Depth
ART_STROKEASPECT
Parameter: Rounding
ART_STROKEROUNDING
Parameter: Growth
ART_STROKEGROWTH
Parameter: Offset
ART_STROKEOFFSET
Parameter: Intermediate Points
SPLINEOBJECT_INTERPOLATION
Parameter: Number
SPLINEOBJECT_SUB
Parameter: Angle
SPLINEOBJECT_ANGLE
Parameter: Maximum Length
SPLINEOBJECT_MAXIMUMLENGTH