Have you tried UpdateAttribute with a new attribute of type array. When each flowfile passes the this processor you could continue to update the value of this attribute by appending a new value to the array, attribute.
However, as @daggett pointed out, it will be helpful if you can provide the input and expected output.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…