By default, the traits assigned to a Sim at the time of creation are meant to be permanent throughout their lifespan. However, there are a few methods you can use to change the traits of your Sims in The Sims 4:
Mods and Custom Content:
Modding and custom content can provide additional options for modifying traits in the game. There are mods available that allow you to change or add traits to your Sims.
Keep in mind that using mods and custom content comes with its own set of considerations, such as compatibility and potential issues.
Potions and Rewards:
The game includes certain potions and rewards that can temporarily change a Sim's traits or grant them new traits.
For example, the "Re-Traiting Potion" from The Sims 4: Realm of Magic pack allows you to change a Sim's traits once consumed.
Cheats and Debugging:
The Sims 4 provides a cheat console that allows you to enable various cheats and debug options.
Some cheat codes may enable you to change traits, but using cheats can have unintended consequences or affect the game balance, so exercise caution.