How to turn off Auto Engine On & Off permanently

I own a 2017 ford mustang v6 automatic. I didn't modify my car and
everything is stock, even the
wheel.

I know there is a drive assist feature that automatically turn on & off engine,
and I know how to turn
it off. But whenever I turn off the feature and come back on the next day, the
feature is check on
again. I want to turn the drive assist feature off permanently.

I understand the auto engine on & off feature is to help
- save battery power
- help people who forgot to turn off their car and walked away
- help engine life

It is just person thing, and I want a smooth ride. I notice when the "auto
engine on & off" feature is
on, a seconds before full stop in low speed, (I don't know what you call it) the
car will crank up a
little bit before full stop. It will not let me have a smooth brake or smooth full
stop.

I did tried the same thing with my "auto engine on & off" feature off. it gave
me a better and smooth
braking before full stop.

How can I turn off the "auto engine on & off" permanently?

Thanks,