Question about Bangle.setUI

I'm a little confused still when you say "you can just create a new Bangle.setUI"

Well, you could add the following code to run at boot - for example via: https://banglejs.com/apps/#custom%20boot

(function() {
  var sui = Bangle.setUI;
  Bangle.setUI = function(mode, cb) {
    if (mode!="clock") return sui(mode,cb);
    sui(); // clear
    Bangle.CLOCK=1;
    Bangle.swipeHandler = Bangle.showLauncher;
    Bangle.on("swipe", Bangle.swipeHandler);
  };
})();

And now Bangle.setUI is overwritten such that for normal clocks, you now swipe your finger to enter the launcher rather than using BTN2.