I have my cameras at the top of the rear window, on a little 5 door hatchback that are hinged / open in the same way, so what i fo is run the wire to one side, and then from there to the C pillar.
This of course mean that when the hatch are closed i have a little surplus wire dangling there.
I could also go thru the rubber grommet where other wires go thru, but i have only done that one time as it take longer to do, and also i change cameras fairly often as a tester so i cant really be bothered going that ultimate route.
You can see the wire loop back there in this frame grab.
Most often the dashcams come with a few stick on wire guides / holders, you could probably also use black duct tape on some parts in your case.
My little car have the rear wiper reaching the very top of the glass, so i can also mount cameras there, but only 2 side by side, as otherwise they are out of wiper range,,,,,,, which are important on a car with a flat " ass"
Also my car are so cheap, that there are no plastic trim around the rear window, so i can mount off the hatch frame itself, i have actually for years used a magnet as a mount / spacer for rear cameras.
