平添píng tiānto add or gain sth without additional effort; to add sth without good cause
錦上添花jǐn shàng tiān huā(lit.) to add flowers to brocade (idiom); (fig.) to make sth good even better; to add an extra (often nonessential) benefit or embellishment
添亂tiān luàn(coll.) to cause trouble for sb; to inconvenience