Is there any way to keep warm like 80F inside the car while plugged in if you are sleeping in it?
I remember from a year ago or so I was waiting for my wife inside the car at a free EV charging station and the weather was kind of chilly (60F).
I tried to use the remote to activate the climate control but it wasn't getting warm. Either that or I may have used the HondaLink app to turn on climate control.

What would be the best way to keep inside warm (or cold) if you were at a camping ground and your car is plugged in a AC outlet?

There are two ways to run heat and AC, neither are perfect for that situation.

Full climate - this is only available when the car is turned on in READY mode, which you can only do when the car is not plugged in. Full climate uses power from the main battery, so it slowly depletes whatever EV range you may have. When the EV range gets down to 0 miles it will start the gas engine to recharge the battery for a few minutes, then it shuts off again. Depending on how much demand you are putting on the heater (or AC) the engine will typically run for a couple of minutes every ten minutes or so. It's not that noisy but it depends on whether you are a light sleeper if you would be able to sleep through the engine briefly coming on every ten minutes. And of course you need to have enough gasoline in the tank, but it doesn't really use that much gas since the engine only comes for brief periods. So much better though than a regular car where the engine has to be running constantly in order to use heat or AC.

Preconditioning - this is only available when the car is not turned on. But you can be plugged in. When the car is plugged in preconditioning draws power from the charger and thus does not deplete EV miles. And with Level 2 you can also charge and precondition at the same time. But preconditioning only runs for thirty minutes at a time then you have to restart it. And it only provides partial heat and AC, as it is designed to just sort of take the edge off so that when you get in the car on a cold day the cabin with be slightly warm instead of freezing cold, and on a hot day the cabin will be slightly cool instead of baking hot. And then when you do turn on the car the climate control can more quickly get the cabin to your set temperature. The main problem if sitting for a long time is you have to keep restarting preconditioning every thirty minutes, not so easy to do if you fall asleep.

Since PHEVS have small batteries, this is not usually a feature they offer.
Some BEVs (like Tesla) offer a "Camp Mode" that does exactly what you are asking. They also have a "Dog Mode" that keeps your pets comfortable if you leave them in the car while shopping, etc.

I assume those modes work while charging? I have sometimes sat in my Clarity while charging and thus could only run preconditioning, which is better than nothing but running full climate would be even better. But then again if it is too cold (or hot) to be comfortable just running preconditioning you can always forgo charging since in a PHEV it's not really necessary. But with an EV you likely really do need to charge if you are stopped somewhere plugged in, so then it makes sense for them to have a mode that allows running full climate while charging.

Get a sleeping bag.

I think Steve Jobs designed Honda's pre-conditioning system. "When the button is pressed the cabin will set to a comfortable temperature" or something like that.

I remember when I first got my Accord Plugin (same pre-conditioning system), I was thinking "how do they know what my 'comfortable temperature is'? Sounds like an Apple product, no configuration, just some suit somewhere that decided what temperature should make you comfortable...

I think that the assumption is that in many cases the car will not be plugged in while you are preconditioning, and so it will be running on HV battery power. The goal then is to warm or cool the car just enough to make it a little more comfortable, or shall we say less uncomfortable than it would be if the cabin was freezing cold or baking hot. But at the same time not draining your EV miles too much, like it would if it went immediately to your set temperature and maintained that for thirty minutes. When you do get in the car and turn on the heat or AC it can get to your personally selected temperature much more quickly after preconditioning.

Although it would have been nice if they had made it so that when you are plugged in it will go to your set temperature right away, since in that case you probably are less concerned about the amount of electricity used, especially if it is free charging.