Harris was born in the ninth season of the original Roseanne series when the show ended in 1997. The last episode was her being brought home from the hospital. In this series, Harris is in high school but in reality she would be approximately 21 years old (at least) when The Conners started in 2018 after the first and only season of the Roseanne reboot.
Neither the last-born Conner child, Jerry Garcia, nor Jackie's son Andy, appears in this series. Jerry Garcia was mentioned by Roseanne's character in the final season of Roseanne (the first and only season of the reboot in 2018) as being away on a fishing boat and not being able to come or phone home. There was no mention ever of Andy or his father Fred, whom Jackie had married and divorced.
After Roseanne was canceled and The Conners started, not even Jerry was mentioned again.
John Goodman, and Laurie Metcalf are the only actors to appear in every episode of Roseanne and The Conners after Roseanne Barr was fired by ABC in 2018.
Roseanne Barr was fired from the show which resulted in her character being killed off, and the series would continue without her. A similar situation happened with Valerie Harper on Valerie/The Hogan Family (1986) when Harper was fired before the start of the third season. Harper's character was killed off the show and the series continued four more seasons without her.
Actor Eric Allan Kramer reprised his role as 'Bobo' in a season five episode, a character he only played in a season one episode of 'Roseanne' that aired in 1989. Which marks the longest gap for any actor to reprise their role in the franchise.