Fade Effect

I ran across same problem and solved it that way until this feature might be available someday:

In your functions.php:

add_action('wp_footer', function() {
	  print('<script type="text/javascript">
	  	(function($) {
			$(".wp-block-cb-carousel").slick("slickSetOption", "fade", true);
			})(jQuery);
		</script>');
	}, 99);

This way you can change the settings of the used Slick-Slider library:
https://kenwheeler.github.io/slick/

You can change the selector .wp-block-cb-carousel to a more specific selector if you want.