Create Custom Metafields: Metafields Custom Field Master Shopify App Review and Tutorial

• After you installed the app and integrated it with your Shopify or Shopify plus account, the app will take you automatically to its main dashboard. 

The dashboard looks simple, a lot better than Metafields manager's. From here, you can choose from Available Resources, such as Shop, product, order, customer, collection, page and blog.

• Start with Page to see how it works. This option has a search button, so there's no need to scroll through thousands of pages. Choose the page you want to edit; in this case, it is the Metafields app. Here you can see some of the meta fields you already made using Metafields manager, and to create a new meta field, click on the blue button that says create new.
• 
  A new window should appear for Metafield creation. Enter Metafield namespace, key description and type. A namespace is used to group different meta fields together logically; if you don't have a lot of meta fields, you can just use local or global.
• 
  To write the instruction for this, start with a key which the name or label of the specific Metafield. A good way of thinking about it is understanding it as an identifier. The description is not mandatory, but it can be helpful if you want to describe your meta field in detail.  
• 
  Now you need to choose the type of Metafield you want to add. If you are using a free plan, you can choose only between integer and string, which is the biggest downside of this app. Work with what you have now, and choose string. Next, there's the value; input this and save it. 
• 
  Going back to the previous page, it's time to see what you have created. From here, you can copy the code, edit Metafield, delete and preview. Finally, grab the code and enter it into your page code. 

Again it would be great if we could just automatically add this code to the desired page or product; this way, you can screw your theme a big if you are not absolutely sure how to do it. 

After you copy the shortcode to the page, it's time to go back to the app to see what else we can do with it. You should note that Import and Export are not available on the free plan. On the free plan, you can add integer or string only.