If you have created a FAQ shortcode preset that you want to show only on one or some specific products, you can easily add it from the product edit page > FAQ.
To show the FAQ tab on the product page, enable the option Show FAQ tab.
Give a name to the tab by entering the text in the field Tab label.
Now select the preset you want to show on the product through the option FAQ to show.
This is an example of the FAQ tab on the product page.