Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Note
TODOWORLD_TASK_NOTEParameter: Move Selected Items to Done
TODOWORLD_DONEParameter: Delete
TODOWORLD_TASK_DELETEParameter: Note
TODOWORLD_DONE_NOTEParameter: Move Selected Items to Task
TODOWORLD_TASKParameter: Delete
TODOWORLD_DONE_DELETE