The attached document contains the macro “Change Shape via Matrix”. It reads the
property “Transformation” from the selected shape, multiplies it with the matrix
(-1 0 0   0 1 0   0 0 1) (read row wise) and writes the result back to the
property. When applying the macro, the shape should flip at the y-axis.
Set a break point in the macro “Examine shape” and watch the object “oShape” to
see this property.

The document contains a custom shape sector object. Select it, activate the
flipping tool from the toolbar, move the mirror axis to the y-axis and flip the
shape. You can watch, that the shape is able to flip correctly.
Reload the document and select the shape again. Click on the icon “Change Shape
via Matrix”. Notice, that the shape is not flipped, but moved.
You can use a classical sector, to proof, that the macro indeed applies flipping
at the y-axis.