How can I solder a 2nd connection to a mini USB?
Soldering them is difficult because the surface mounts are very tiny, it requires steadily holding the wires in place, and since the area is so small, the solder crosses over to the other surface mount areas.


SMD soldering requires a non-trivial amount of training (and flux). You don't want to train on stuff that needs to be in working condition.

And even if you manage to solder wires to these SMD pads, the result will be rather fragile.


  If there is any way, It would be really helpful if the mini USB was still functional


USB requires a hub once you wanted to connect more than one device to a port.

Also, USB 2.0 high speed data lines are quite sensitive to impedance mismatch, so even just soldering your additional wires could cause USB malfunctions.