Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Regular Pulse
VIBRATEEXPRESSION_REGULARParameter: Relative
VIBRATEEXPRESSION_RELATIVEParameter: Seed
VIBRATEEXPRESSION_SEEDParameter: Enable Position
VIBRATEEXPRESSION_POS_ENABLEParameter: Position Amplitude
VIBRATEEXPRESSION_POS_AMPLITUDEParameter: Position Frequency
VIBRATEEXPRESSION_POS_FREQUENCYParameter: Enable Rotation
VIBRATEEXPRESSION_ROT_ENABLEParameter: Rotation Amplitude
VIBRATEEXPRESSION_ROT_AMPLITUDEParameter: Rotation Frequency
VIBRATEEXPRESSION_ROT_FREQUENCYParameter: Enable Scale
VIBRATEEXPRESSION_SCL_ENABLEParameter: Uniform Scale
VIBRATEEXPRESSION_SCL_UNIFORMParameter: Scale Amplitude
VIBRATEEXPRESSION_SCL_AMPLITUDEParameter: Scale Frequency
VIBRATEEXPRESSION_SCL_FREQUENCY