I'd imagine it uses the parks to flash when locks and unlocks. It should be the Red/Blue right beside a Green/Red, pin 11 of the switch connector. See EL-47 here (pdf page 933):
https://www.nicoclub.com/service-manual ... _240sx.pdf

Thank you!

After testing the two red/blue wires I found behind the dash with a multi-tester and verifying that they output 12v when the parking lights were turned on, yet not having the parking lights flash when I connected the white or white/brown wires from the Viper's main harness, I read the Viper installation manual and noticed that I didn't install the fuse!

It now seems to work correctly. This is my set-up after reading more carefully.
1. The fuse is positioned in the (+) position in the light flash polarity jumper.
2. Only the white "parking light output" wire from the Viper's main harness is connected.

I'm not using the white/brown "parking light isolation wire - pin 87a of onboard relay." The Viper 3606V manual says this "is used for vehicles requiring light switch isolation during parking lights flash output."

Is my set-up appropriate (i.e., fuse in [+] position, only white "parking light output" wire connected)?

That should be good, I don't see any reason to isolate the parks electrically. Your SXy is an old ride with switches and relays, it isn't like there any microcontrollers involved that need to be protected. Just the Timer Module, and that isn't really a micro, just a collection of CMOS timer circuits. Unless you discover any functional issues, it should be fine the way you wired it.