I have 1100 miles on my 2020 Ascent.

When the temp drops below 45 degrees I notice the cold start idle is around 2600 rpm for a while. That seems excessive. Also, the CVT when shifting from reverse to drive studdered as it took off. Again, these are only when it is cold. AFter it warms up, all is well as I am use to with my Subaru CVT experience.

Anybody else experience this?

2500 ish' is a normal high idle warm up RPM....my outback does that...if your dropping it into reverse at that RPM before letting it warm up and idle speed settle down then its normal for the gear transition to feel more aggressive. Let it warm up for a few minutes and idle should start to come down, or blip the throttle before going into gear to drop the idle down faster.