Sometimes when you copy-paste a table from another source into your document in Web Manuals the border table icon is greyed out and you cannot click on it.
In order to make this symbol (Table borders) to be active again, you need to take the following steps:
1. Right-click on the table
2. Click on Table Properties
3. Set border size to 0 and press OK
4. Then you will see this feature appear and you can start using it again