I'm not entirely sure it's that simple to be honest with you.
I scavenged a VSC Off switch from a Tacoma years ago (maybe it was a 4th Gen, honestly it doesn't matter) and plugged it in to see if it would work. Unfortunately it did not, looking at the wiring diagram it seems to simply send a signal to the CSW terminal on the ABS/VSC/TRAC module. In the EWD for '03-'04 it's labeled as a "TRAC OFF" switch and comes off Pin#26 (Connector S8) of ABS Module and is only present for 2WD models. In '05-'09 models it's still using the CSW terminal but on Pin#43 (Connector S28, the pinout changes are likely due to the changes in the physical ABS module from '03-'04 to '05-'09) and the switch has been renamed to "Auto LSD," again only present on 2WD models. The "New Car Features" section for the 2003 model year shows that the TRAC Off Switch is a 2WD only option.
There is not much more documentation beyond that honestly. Toyota doesn't let you reprogram or modify much on ABS modules, the only exception I can think of is early 1st Gen Sequoias we had a recall on. The ABS module is basically hard coded and that's that. So based on the information on hand and my gut feeling, even if you went and wired a momentary switch to the CSW pin on the ABS module (in case the wiring doesn't fully extend back to the ABS module even though you have the connector at the dash panel) it will probably still do nothing because the 4WD ABS Module does not have the logic to do anything with that input signal.
I could be wrong on that because it has been about 6-7yrs since I tried to make that work and ultimately it went on my list of "get around to it projects" along with using a factory RSCA Off switch to disable the entire SRS system. So if anyone has made it work, I'd appreciate the correction.
But if you do want to basically disable the entire ABS/VSC/TRAC system you could use a factory switch or a switch to basically disconnect an ABS Wheel speed sensor. I know a lot of members have had luck with simply unplugging the brake master cylinder pressure switch also; I personally had finicky luck with it when I did actually need to kill the system on a trail a long time ago (hence the reason I tried the switch.) Based on Toyota's internal flowchart from the new car features (there's oddly a lot of interesting information in the NCF that doesn't show up anywhere in the FSM for the 2003 model or any of the 4th gen model years... Why Toyota? Why do you do this to us?) the easiest way to completely disable the system is to just kill a wheel speed sensor, the "hardest" fault to get the system to disable itself is to set a DTC for any of the wheel speed sensors or internal ABS Solenoids. You can hijack a wheel speed sensor signal from the driver's side junction connectors. It's a one-trip system so once you reconnect the signal the system will clear the fault on the next key cycle after driving a short while. It's how a couple people I know wired they're VSC/TRAC Kill switches. I plan to do this eventually, so I'll probably make a post on it if I do.
Apologies on the long post, I'm sure it's more information than you really wanted; but hopefully it answers your question.