Left Rear Wheel Well -- how does this clip work???

They’re very tricky to get off, likely the “official” method to remove is to just destroy the locking jaws and replace. Anyway:

There’s two jaws, diagonally opposite in a square pattern. I used a pin in the centre hole, trying to catch the end of a jaw, press it toward the center, while prying up on the fastener’s flange at that same zone.

If you’re successful in releasing the jaw, the flange will stay a little raised. Keep something in the gap and repeat the process on the diagonally opposite jaw.

it helps to be myopic, and/or use good reading glasses and good light. Still you’re mostly going by feel. I believe one of the two you can see ‘round the back, get a better understanding of how the jaws are oriented, maybe even release one of the jaws.

 

I think:

90189-06145

Here:

https://www.amayama.com/en/genuine-catalogs/epc/toyota-usa/prius/ZVW30L/13501/body/5202

Googling the part no, yeah that's the baby. Good pics too, help for coaxing them out.

 

Get some stiff wire, paperclips in there - they'll act like 'ramps' as you pry them out????
You may still destroy them, but it's worth a shot.....

 

In the left-side thumbnail, you're squeezing the jaws together with your fingers? That's basically the release trick, get something through that hole, pressed on the jaw head, push it towards the center, simultaenously prying the flange on that side. Keep that flange lifted (can take a few tries), then repeat on other side, which usually goes slghtly easier.