In order to display descriptions for your product variations in Product Table you need:

In the Add Products Wizard, display the variations as separate products (show variations checkbox), and add the ones you need to the table.

Now descriptions will be displayed in the Summary column.

Except that, you can also enable the popup description functionality for the summary column.  To do that, you need to open the column settings and in the opened window check the Description popup option. 

If you go to the Settings >> Features path, you can toggle the Show variation description instead of the product description option to show variation description instead of product description in variations popup.

If you need to change the size of the popup, scroll to the Features section where you\’ll find the Popup size option. You can set the size either in % or px.