USB Charge and data separate cables
Yes, but not quite what you suggest.

You would have to feed D+/D-/GND to the PC, not just D+/D-. This would allow the PC to communicate without supplying power.

It's then possible to split off the +5V cable and GND to an external +5V power supply. In order to do this, you would need to split open the cable where you want to splice off your power supply, preferably without damaging the D+/D- cables as these are controlled impedance and don't particularly like having random bits of cable or solder joints in them.

Once the outer insulation is split open, you can remove a small section of insulation from the GND cable and solder on the GND from your second cable. Then also cut the +5V cable and solder it instead to your second cable.

Finally, carefully cover everything up with heat shrink tubing or similar.

Basically you would have something like:



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