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.
Yeah, exactly.
Cable management is for three reasons: airflow, maintainability, and aesthetics. None of those are needed here, so just put the case on and call it good.
Computers of this era weren’t meant to be looked at!