However, this did not work for me. I tried setting it to 1, which did work to make “No” the default button. So, I assume -1 not working must be a bug. I will get this submitted and we should be able to fix it.
I confirm the button is correctly parameterized by the -1/+1 but no change with the keyboard input.
The default button is always validated par the “ENTER/RETURN”
Thanks for reporting the bug.