Live up a mountain, loooong haul back home from town at sea level, and regularly towing a heavy trailer.

Is a add on transmission cooler worth it? These were my stats getting home today... and i was taking it easy.

I'd not be overly concerned about a it. It's only a few degrees over the coolant temperature. Auto trans fluid is quite happy at 150° C or more for short periods. Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.

I'm not a transmission tech but that doesn't look awful to me. I'd be looking at the oil on the regular to see if it's dirty or burnt, and if it's degrading faster than you're comfortable with then consider a change. From what little I know the plate coolers are pretty efficient compared to the old 'hanging out in the breeze' style.

It is a cool display though: am I right in presuming it's some sort of OBD dongle and an app like Torque running on an Android phone?

Thanks guys, I won't stress too much then.

Yes, exactly that! Bluetooth OBD dongle and Torque app.

Naw, temps look fine to me.

I've towed max GW in the western mountains in the US in the summer (8,000ft+, 40*C) and while the cooling system on the 3.2 i6 eventually sprung a couple leaks the tranny is still fine at 180k miles (fluid changes every 40K).

I do monitor it to keep temps under control.