How would you go about creating this sound effect?

There are a lot of things going on.

Which sound? The fast tremolo keyboard thing? The pluck the string on the headstock? The fast muted chug?

Something else?

My guess is that the other guitarist, with the Les Paul Standard, palm muted, and played it with his pick.

It's called a "kill switch" effect. I'm adding one to one of my floyd rose strats.

Check out the videos...

https://ironageaccessories.com/collections/about-killswitches

You can try programming a Kill Switch like this, but, no one's foot is as fast as their picking hand:

Morph Rig Volume down to nothing. Set the Rise and Fall time to Zero.

Use a Morph foot switch instead of an expression pedal. Set the Morph foot switch to Momentary.

Tap that footswitch really fast

Or wait until we get an updated tremolo effect with a square wave

maybe a delay, one 16th note, no decay and a wahwah?

Quote from christianbad

maybe a delay, one 16th note, no decay and a wahwah?

16th note delay with high feedback so it goes into oscillation, exactly as loud as the original note, just pick the first one.
The Dirt parameter will help here, too

A "slicer" effect ?

Or is it done with keyboard? I se a Moogerfooger (?) to the left on the keyboards @ 1.46 .....

Just a thought

Cheers !

Quote from Ruefus

Can’t be a kill switch. Too fast for feet, his hands are nowhere near a button. Plus, the sound feeds back on itself before he turns it off.

Square wave tremolo? Hmmm….maybe with some delay to get it to self oscillate?

He has a soundman in the back on the switch. Don't you guys know those "live" tricks of the trade?

Looks like he turns a pedal on with his foot to me. My bet is a square wave tremolo. Be very easy to create this sound with a fulltone supa trem for example.

Post your result when you've done it.