This task is horrible and filthy.
By chance, does anyone have a little trick to accomplish
this fun little task ?

Put a small hose clamp around the cable to compress the retainer deal until it passed through the backing plate then remove the clamp.
Gus

Or you can slide a box wrench down the cable to depress the "fingers".

Or a piece of tubing or a 12 point socket over the end of the cable.

Push on while twisting it......

I always shove a screwdriver in there and break the clip off. Usually because when I'm removing it the same cable isn't going back on.

That's how I do it too.
A little wiggling and it pops right out.