Paul wrote:

If the pins could be backed out of the shell, that would solve
one part of the puzzle. Some shells have a "tab per pin", and
releasing the tab with a hobby knife, allows the wire and pin
to be extracted. The pin will have a "spike" on the side of it,
which catches in the tab, to hold it secure. Things like that
are intended to be "one way" insert. If the thing the pin
lodges in, can be released, then the pin can be backed out.

I find a small sewing needle works to depress the locking finger. It's
metal is stronger than just a pin. However, once the pin is out of the
connector shell, it is improbable the wire can be removed from the
crimped pin without damaging the pin. The metal becomes weak and breaks
when you try to uncrimp the part holding the wire. Soldering would
require a very small tipped iron and the soldered joint would have to be
small enough so it fits into the connector's hole into which the pin
slides.

You can unsolder the mating connector from the Contour PCB.
Then solder the wire, right to the PCB. That may be the
most practical solution. It really depends, on what you envisage
as the assembly order, and whether the cable arrangement can
be set up, before the soldering begins.

I suspect even easier would be to cut off the connector on the wire
bundle and solder each wird underneath the PCB - if the wires are long
enough. Rather than try to remove the PCB connector and solder there,
just solder onto the other side.

The black part is just heat shrink tubing that could be cut away. The
strain relief (plastic blob) around the cable may be molded and not
reusable. If this is the case, you want that use custom strain relief
(you find anything else that works with that mouse shell). If it's a
molded blob on the cable, and because you must use it to prevent the
soldered wires from getting yanked on at their solder connection,
lengthening the wires is needed. Solder a short length of wire onto
each existing cable wire. The old and new wires are braided so unbraid
them to straighten, mesh the ends together, twist a little, and solder
the wires inline with each other. You end up with a short length of
bare meshed wires. Slide over some heatshrink tubing just a bit larger
than the soldered wires and heat to shrink. Now the wires will be long
enough to route to the other side of the PCB to solder them there.

Unless it looked easy to get the pin out, remove the wire from the pin,
solder on new part of the old wire (trim it back), and the soldered job
still fits into the connector, I'd just give up on reusing the
connector. Solder wire stubbies onto the solder pads on the other side
of the connector (you could remove the connector using a solder sucker
or wick but removal might not be needed) and run them around the PCB to
solder them to trimmed old wire(s). Be sure to slide the heatshrink
over the stub or old wire before soldering so it's available over the
wire to slide over the solder joint to heat and seal it.