Слайдер «до/после» в Tilda
готовый код.

<div class="tselno-compare" style="--position: 50%">
  <img class="tselno-compare__image" src="BEFORE_IMAGE_URL" alt="До">
  <img class="tselno-compare__image tselno-compare__after" src="AFTER_IMAGE_URL" alt="После">
  <span class="tselno-compare__label tselno-compare__label--before">До</span>
  <span class="tselno-compare__label tselno-compare__label--after">После</span>
  <span class="tselno-compare__line" aria-hidden="true"></span>
  <input class="tselno-compare__range" type="range" min="0" max="100" value="50" aria-label="Показать результат до или после">
</div>

<style>
.tselno-compare {
  position: relative;
  overflow: hidden;
  width: 100%;
  aspect-ratio: 16 / 10;
  background: #ddd;
}
.tselno-compare__image {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
}
.tselno-compare__after {
  clip-path: inset(0 calc(100% - var(--position)) 0 0);
}
.tselno-compare__line {
  position: absolute;
  top: 0;
  bottom: 0;
  left: var(--position);
  width: 2px;
  background: #fff;
  transform: translateX(-1px);
  pointer-events: none;
}
.tselno-compare__line::after {
  content: '↔';
  position: absolute;
  top: 50%;
  left: 50%;
  width: 48px;
  height: 48px;
  display: grid;
  place-items: center;
  border-radius: 50%;
  background: #fff;
  color: #10110f;
  transform: translate(-50%, -50%);
}
.tselno-compare__range {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  margin: 0;
  opacity: 0;
  cursor: ew-resize;
}
.tselno-compare__label {
  position: absolute;
  z-index: 2;
  top: 16px;
  padding: 8px 10px;
  background: #10110f;
  color: #fff;
  font: 700 12px/1 Arial, sans-serif;
  text-transform: uppercase;
}
.tselno-compare__label--before { left: 16px; }
.tselno-compare__label--after { right: 16px; }
</style>

<script>
document.querySelectorAll('.tselno-compare').forEach(function (compare) {
  var range = compare.querySelector('.tselno-compare__range');
  range.addEventListener('input', function () {
    compare.style.setProperty('--position', range.value + '%');
  });
});
</script>