You cannot find these strings by playing the game normally. You need to extract them. Here is the technical workflow used by the modding community:
Over the years, the modding community has cataloged hundreds of exclusive strings. Here are the most famous "easter eggs" hidden within the raw localization data. sims 4 language strings exclusive
For , language strings are managed through String Tables (STBL) which consist of unique Keys (hexadecimal codes) and Values (the actual text). You cannot find these strings by playing the game normally
By searching for Trait_Exclusive or similar debug tags, modders have uncovered references to traits like: sims 4 language strings exclusive