With the product-specific custom field "Custom tab – Text" you fill the "Custom tab" on product pages. If you leave this field empty, no tab is displayed for this product.
The input field is HTML-capable, so you can format the text as you like.
Note: You can enable/disable the "Custom tab" in the theme configuration.
You can find the "Custom tab – Text" custom field in the respective product:
Tab "Specifications" ⇒ Block "Custom fields" ⇒ Tab (Set) "Products (ThemeWare® ... Pro)"
Type: Text editor (HTML)
Technical name: twt_{theme}_{edition}_custom_field__product__custom_tab_text
You can find more information about the "Custom tab" extension here: