JSFiddle - React, Tailwind, and code Playground

HTML

<div class="caldera-forms-modal">
  [caldera_form_modal id="CF5adb0684df741" type="button" width="500"]<i class="x-icon x-icon-envelope" data-x-icon="" style="font-size:20px">　문의하기</i>[/caldera_form_modal]
</div>
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<div...

CSS

.caldera-forms-modal {
  	visibility: hidden;
  	color: white;
    background-color: #d65b5b ;
    border: 1px solid #d65b5b;
		border-radius: 5px 0px 0px 5px;
  	height: 40px;
  	width: 150px; !imporatnt;
  	position: fixed;
  	z-index: 9999;
  	float: right;
  	right: -104px;
  	bottom: 2%;
		transition: right 0.3s;
}

.caldera-forms-modal:hover {  
   	right: 0%;
}

.caldera-forms-modal.shown {
  visibility: visible;
}

JavaScript

/** javascript, jquery **/
$(window).scroll(function() {
  var $el = $('.caldera-forms-modal');
  
  if($(this).scrollTop() >= 300) $el.addClass('shown');
  else $el.removeClass('shown');
});
/** end **/