Thanks lifespeed.
Some people have tried holding the 3 buttons down as first described and achieved what you desire...to manually disengage the AC compressor while in Defrost mode.

It seems that some cars are different because I tried the 3 button procedure and nothing happened.
I tried it over & over without any luck.

However I was successful in AutoStop while in Defrost mode.

It occurred to me after I made the post here on the 23rd that I never tried holding down the A/C button and the ECON together.
Later that evening I tried holding those 2 buttons down and the light on my A/C button flashed 7 times. It worked on the first try. I can now manually disengage the A/C while in Defrost mode using the A/C button.

Efficient drivers do it better.
1003 miles a tank personal record. 74MPG calculated. HCH1 CVT