New to High Mileage Prime, Looking for Long Term Maintenance Items

Long time lurker, long relied on the maintenance schedule spreadsheet @Mendel Leisk prepared on an older gen 2 and am forever grateful. Knock wood, never had mechanical issues on it, mileage was modest tho. Oil changes, replaced radio knob with a 3d printer one, and notably at higher miles I did:

1. spark plugs
2. Trans fluid
3. Coolant
   
4. Serpentine Belt

I know, read the manual!!! Looking at the 2020 Prime booklet, looking very familiar: regular oil / filter changes, 100k engine/inverter coolant change and 120k spark plug changes. Like with earlier models, no mention of trans and serpentine.

I bought a 2020 Ltd for safety features and hoping for long term reliability, but paid accordingly for one w/ 140k+ miles on it and an incomplete service history. On the one hand, I assume given the new age coolant, trans, plugs, belt should be in good shape given they're only ~4 years old.

Is there any way to check if coolant has been done in past (nothing is in Carfax/svc logs)? What say you re: trans fluid and serpentine on a Prime? I want to be proactive so that this car lasts as long as I know Prius' are able to!!! Notwithstanding the tech (feckless 11" screen, lack of android auto, awful app), I love everything about the car itself.

 

Thought I had poured through the forums a fair bit over the past few days, but finally found the pertinent trans fluid threads
My Prime's first transmission fluid change | PriusChat
Seems to still be subject to owner opinion on when to change this lifetime fluid, only consistent confirmation that it is dirtier than expected in 1st change which some doing in first 5k mi! And then thereafter it is comically clean (some doing 30k, others 60k+ intervals)

Also, I think the reason I didn't find anything on the belt is... there is no more belt . I get there is no serpentine but thought there would still be some belt or chain (was thinking AC but guess heat pump alleviates that too).

Sorry for not having done more thorough digging initially