How do we change the VDDA1,2 supplies? Other than directly supplying an external voltage to either VDDA1 or VDDA2 pins in the nucleo hat.

Assuming that most people want to set VDDA1 and VDDA2 to 3.3V (the same as VDDIO on the padframe), there's a header (or holes for a header) across the bottom of the hat where you can jumper VDDA1 and VDDA2 to the "3V3" pin next to each one.