Magento 2.1 – Display Category Title on Category Page

In my case it wasn't working because the inserted value was starting with a blank space. Try to trim the suffix. Ex "- my website" instead of " - my website" Hope it helps

Better idea create a custom module for this.

This module must have below files:

• app\code\[VendorName]\[ModuleName]\composer.json
• app\code\[VendorName]\[ModuleName]\registration.php
• app\code\[VendorName]\[ModuleName]\etc\module.xml
• app\code\[VendorName]\[ModuleName]\Block\Categories.php

On block class, you should create category collection filter and filter that collection by your 6 category ids

<?php
namespace [VendorName]\[ModuleName]\Block;
class Categories extends \Magento\Framework\View\Element\Template
{

  protected $_categoryCollectionFactory;
  protected $_categoryHelper;

    public function __construct(
        \Magento\Backend\Block\Template\Context $context,        
        \Magento\Catalog\Model\ResourceModel\Category\CollectionFactory $categoryCollectionFactory,
        \Magento\Catalog\Helper\Category $categoryHelper,
        array $data = []
    )
    {
        $this->_categoryCollectionFactory = $categoryCollectionFactory;
        $this->_categoryHelper = $categoryHelper;
        parent::__construct($context, $data);
    }

    public function getCategories()
    {
        $collection = $this->_categoryCollectionFactory->create();
        $categoryIds = array(CatId1,CatId2,...CatId6);
        $collection->addAttributeToFilter('entity_id',array('in',$categoryIds));
        return $collection
    }
  }

Then use this new block instead of Magento\Framework\View\Element\Template.

See idea how use block class at http://blog.chapagain.com.np/magento-2-get-list-of-all-categories-store-categories/