I am Sephardic and I know that my Minhag is to put on a Tzitzit and tuck them in. I wanted to know if it’s okay to wear another Tzitzit over my shirt. Since I’m fulfilling my Mitzvah already by tucking my Tzitzit under my shirt. Thank you.

ב"ה Shalom As you said , the custom of Sephardic Jews is to have the garment of the Tzizit and the fringes themselves tucked in and not seen, as Rav Chaim Vital wrote in the name of the Ari z"l, that it is a great mistake to have the garment of the Tzizit on top of the clothes. ( and then explained by many that this included the Tzizit fringes as well.) Therefore, wearing another garment of Tzizit would be against the Sephardic custom. See יחווה דעת חלק סי' א, ילקוט יוסף סי' ח, ס"ק מ"א All the best