How to add short descriptions?
The first you need install extension on your chrome browser by go to this link: http://shopifyfd.com/. After complete installation you can see shopifyFD icon in your browser like below screenshot.
Now go to store admin > products > open product page, Then you need click to ShopifyFD icon and metafield box will appear on page.
value: Add your text or HTML code here for show ad short descriptions.
Save details by click on “save” button available in metafield box.
Do not use product page save buttons to save this data. If by mistake click on product page save button then refresh page and follow steps from start.