Adding a subtitle to a specific table column

Hey Anonymous 
A simple workaround solution to your requirement is adding small more information icons from add button menu

and set the action type as "web URL" and keep the "Web URL" field empty, lastly add a description that you want to display while your user hovers in the tooltip text.

Now you can place this button on the column field where your user is going to hover.

If this helps you please mark my solution as accepted so that other users can find it quickly when facing a similar issue. Thank you!