I finally got it working, like this:
Once the button (with class="prev") is clicked:
$(document).on('click', '.prev', function() {
// If it is the first slide...
if (mySwiper.activeIndex == 0) {
// Slide content
var slide = '<p>New slide</p>';
// Creation of the slide (it instantly moves to index 0 --> the new slide)
mySwiper.prependSlide(slide);
// And then instant (speed = 0) swipe to slide with index 1
// (the one we were watching before creating the new...)
mySwiper.swipeTo(1, 0, false);
// Finally, we implement the visual transition to new slide (index 0)
mySwiper.swipePrev();
}
});
I hope it helps somebody. Thanks.