The pc does not have back compartment, nor anyway to attack the cable to. What I am thinking right now is to hot glue some zip ties to the centre gap between HDD and mb. And then zip ties the cable to the zip tie, so it runs down the centre of the pc cleanly and branches out to its destination like a upside-down tree.
I hope when you say “hot glue zip ties”, you mean hot gluing a sticky zip tie mount such as this
Otherwise you’re a monster :p