JSFiddle - React, Tailwind, and code Playground

HTML

<div id="block-items">
  <div class="item-block">
    <input type="button" value="Кнопка 1" class="item-button" data-index="1">
  </div>
</div>

JavaScript

var buttonEvent = function(){
	var button = $(this);
  var index = button.data('index');
  var block = button.parent();
  if (!this.nextElementSibling){
  	$('<span class="item-text">Пункт ' + index + '</span>').insertAfter(button);
    index++;
    $('<div class="item-block">' +
    	'<input type="button" value="Кнопка ' + index + '" class="item-button" data-index="' + index + '">' +
  		'</div>').insertAfter(block);
    $('div.item-block:last input.item-button').unbind().on('mouseover', buttonEvent);
  }
};

$('div.item-block:last input.item-button').unbind().on('mouseover', buttonEvent);