Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Strength
MGTARGETEFFECTOR_STRENGTHParameter: Selection
MGTARGETEFFECTOR_SELECTIONParameter: Target Mode
MGTARGETEFFECTOR_MODEParameter: Set Weight
MGTARGETEFFECTOR_SETWEIGHTParameter: Target Object
MGTARGETEFFECTOR_OBJECTParameter: Use Pitch
MGTARGETEFFECTOR_PITCHParameter: Reverse Heading
MGTARGETEFFECTOR_REVERSEVECTORParameter: Up Vector
MGTARGETEFFECTOR_PRIMITIVEAXISParameter: Object
MGTARGETEFFECTOR_UPParameter: Repel
MGTARGETEFFECTOR_REACTParameter: Distance
MGTARGETEFFECTOR_RANGEParameter: Distance Strength
ETARG_RANGE_STRENGTH