In The Sims 4, it is possible to modify any sim in your neighborhood once you start the game.
You can add sims to your currently family, you can change motives, happiness.. even teleport them around the neighborhood.
There are a couple commands you have to enter before you can do this however.
How to Edit Sims in The Sims 4
First you need to access the Sims 4 cheat console.
To pull up the console, hit Ctrl+Shift+C (or Cmd+Shift+C on a Mac) on your keyboard.
Once the cheat console is up, type in testing cheats true and hit enter.
Once Testing Cheats is turned on, type cas.fulleditmode and hit enter.
Once that is done, you’ll be able to shift click on sims, which will pop up additional options in the menu.
Shift Click on a Sim
Add to Family: Add selected sim to the current family
Cheat Motive – Disable Motive Decay: Motives don’t change
Cheat Motive – Enable Motive Decay: Motives change dynamically (default mode)
Cheat Motive – Make Happy: All motives are set to full and mood is set to Happy
Modify in CAS: Allows sim to be modified in the editor, except for their name and inherited traits
Reset Object: Reset the sim back to default state
Shift Click on the Ground
Teleport Here: Move selected sim to that location (only sims you have control of)
More Cheats for The Sims 4
Check out my Cheat Codes list for The Sims 4 if you are in need of more cheats.