Faster Pulses with Spare Timers?

Finally got around to this, and results are excellent. Getting <0.3us jitter.
The examples definitely came in handy, although there's a bit of guesswork involved in sending the right values to the right places.

A working example is included below though that uses a button on D17 to start / stop a train of pulses.

var ll = require("NRF52LL");
// 100Hz pulses of 20us width, but triggered by button press.
// Set up D20 as output
digitalWrite(D20, 0);
// Create a task for the pin
var t0 = ll.gpiote(7, {type:"task",pin:D20});
// Create a timer using timer 2 that counts to 10000
// and has capture-compares at 20 and 10000 counts.
var tmr = ll.timer(2, {cc:[20, 10000],cc1clear:1});
// User a PPI to trigger the events.
ll.ppiEnable(0, tmr.eCompare[0], t0.tClr);
ll.ppiEnable(1, tmr.eCompare[1], t0.tSet);
//Button stuff to start/stop pulses.
let btn = false;
function checkBtn(){
    if (digitalRead(D17) == 1) {
        if (btn==false){
            // Manually start timer
            poke32(tmr.tStart,1);
            while(digitalRead(D17)){}
            btn=true;
        }
        else{
            // stop the timer.
            poke32(tmr.tStop,1);
            while(digitalRead(D17)){}
            digitalWrite(D20, 0);
            btn=false;
        }
    }
}
setInterval(checkBtn, 10);

edit - added 'var ll = require("NRF52LL");' at top of example