In his Manual of the Practice, Procedure and Usage of the Legislative Council of South Australia (quoted by Edwards in the 1938 MS), Blackmore made the following comments about amendments to amendments:
The proposal to amend an original Amendment creates in effect a new Question, and is so treated.
The original Question under consideration is laid aside, and the Amendment becomes, so to speak, a substantive motion to which an Amendment is proposed.
By this procedure all confusion is avoided, such as would occur if the main Question, the Amendment thereto, and the Amendment on the Amendment, were under consideration together.
This sensible practice also underpins a clear right to speak on each new question enumerated in a detailed ruling by President Baker (see commentary on SO 188).
The questions are resolved in reverse order of their being moved:
the amendment to the amendment
the amendment (possibly as amended) to the motion
the motion (possibly as amended).