One or double click the button and time duration for long or short press?

Unless I'm totally misunderstanding, you need to actually check the value in theisLong variable and do something with it, rather than having 2 watches:

setWatch(function(e){
    var isLong = (e.time-e.lastTime)>0.4;
    print(isLong.toString());
    if (isLong) onD23();
    else offD23();
  }, BTN, {repeat:true, debounce:50, edge:"falling"});

function onD23(){
  console.log("onD23");
  digitalWrite(D23,1);
  setTimeout(function () { digitalWrite(D23,0); }, 1000);
}
function offD23(){
  console.log("offD23");
  digitalWrite(D23,0);
  setTimeout(function () { digitalWrite(D23,1); }, 1000);
}

It's still going to get a bit confusing though - it'd be easier to check if you had 2 different LEDs.