[TLDR] I made a modification to my RCS Tools folding lock pick set to help retain the tension wrench, which could easily pop free without warning. [/TLDR]
The edge of the tension wrench is visible along the bottom of the tool.
A small rivet (visible along the leftmost edge of the tool) was added. A desktop drill press with a #62 (.036) drill bit was used to make the hole.
(This hi-speed rotary tool was too fast by far for drilling such a tiny hole in plastic, but our floor drill press would pretzel such a tiny bit, except that carbide bits would actually shrapnel and fly across the shop, as opposed to actually pretzeling.)
I created the pin from a piece of aluminum wire by cutting it to rough length. I used short nosed, smooth-jawed pliers to hold the wire so it was perpendicular to the edge of the plier jaw -- this helps me to not sand my pliers. I shortened the wire to just a hair too long, and squared the ends off.
I rolled the wire between iron plates to straighten it out -- next time I'll do this step before sanding the wire down, since the wire was so short it kept going sideways.
I used a digital micrometer to get the diameter of the wire, and selected the right bit for the Dremel press. This was maybe .001 under the diameter of the pin for a snug fit.
The pin is visible at the left end of the tension wrench,
right inside the channel and next to the red handle.
I added the pin where it won't interfere with pick rotation or use, and it seems to have enough plastic around it to avoid breaking out. The wire bent slightly when i tapped it down flush with a steel hammer because i didn't give it enough support in the middle, but it didn't crack or damage the case and it retains the wrench properly, so I won't rework it just for a blemish defect.
(EDIT: I ended up finding a dowel pin in my junk box and re-drilled, inserting the nice steel pin in place of the nasty old aluminum one. Happily ever after.)
The wrench is definitely retained securely and will only come out when it's needed.