Matthew J. Fahey, principal designer for The Sims 4, has confirmed that simmers will be able to edit their sims’ body scars at any time in Create a Sim, not only when you first make a sim. This feature will come in a future update. See his tweet below.
Body scars were added as a new category in CAS back in June of 2022, on the patch that prepared the game for the Werewolves Game Pack. A new scar was added on the January 2023 game update, for top surgeries.
— Matthew J. Fahey (@Mattnetic) February 7, 2023