I had planed to extent the TTL flash cable for my Olympus camera - external flash.
And I like to share my odyssey , yes I had one ..

First of all I got several male Mini Din , with wrong in diameter center plastic pin,
some one had flood the market with damn cheap bad made, male ones.
As soon I found one good set of three males , I was able to move on..
At the process of soldering , I killed the first male Mini Din , due high temperature at the soldering station.
No one ever advices , how much temperature to use ,
when you work with those small and sensitive plugs !!
The best tip that I have to offer , are to have the male & female hooked together, when you solder the cables on it.
About how to correctly lock the small metal clip on the cable ( anchor ) ,
its best to install the metal clip in the hole of the plastic inner body first, then to put above the cable with the soldered plug , and to use an common plier, and press the plastic bottom with its end of the metal clip.
It gets a nice curved shape that way.
Pictures ..