In my experience, sometimes it is there, sometimes it is not. So wait a few days and try again if you don't see "lugagge" icon when you look up your reservation on TAP webpage.

It is def. possible to add luggage for 1 pax only. Did this in June on the TAP webpage; OTA booking as well.

As a last resort you can add it during OLCI (although it will be slightly more expensive than if you do it before OLCI opens).

Please note that the price for add. luggage remains the same so there is no hurry; you can do it until OLCI opens without paying more.