Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Mode
MDATA_KNIFEPLANE_MODEParameter: Plane Mode
MDATA_KNIFEPLANE_PLANE_MODEParameter: Plane
MDATA_KNIFEPLANE_PLANEParameter: Plane Position
MDATA_KNIFEPLANE_PIVOT_POSITIONParameter: Plane Rotation
MDATA_KNIFEPLANE_PIVOT_ROTATIONParameter: Offset
MDATA_KNIFEPLANE_OFFSETParameter: Number of Cuts
MDATA_KNIFEPLANE_CONUTParameter: Spacing
MDATA_KNIFEPLANE_DISTParameter: Restrict To Selection
MDATA_KNIFEPLANE_SELECTEDParameter: Select Cuts
MDATA_KNIFEPLANE_SELECT_CUTParameter: Connect Cut Edges
MDATA_KNIFEPLANE_CUTPOLYSParameter: Preserve N-gon Curvature
MDATA_KNIFEPLANE_NGON_CURVATUREParameter: Auto Snap
MDATA_KNIFEPLANE_AUTOSNAPParameter: Regular Slice
MDATA_KNIFEPLANE_REGULARSLICEParameter: Angle Constrain
MDATA_KNIFEPLANE_ANGLE_CONSTRAINTParameter: Angle
MDATA_KNIFEPLANE_ANGLE_CONSTRAINT_VALUEParameter: Realtime Cut
MDATA_KNIFEPLANE_REALTIME