@DystopianViolet When you create a new household, you can add a Sim from your library and as long as you are still in the initial household creation you will still be in full edit mode.
I’m referring to after creation though. Sometimes it takes while of playing the game before it’s clear what traits will be useful. Apparently you can change aspirations organically, but it doesn’t appear that it changes the character’s behavior.
@DystopianViolet Every time you create a new household, it's saved to your library. If you want to re-save a household you've been playing with for a while, you can do this from CAS by clicking the "Save Household" folder icon. You won't keep personal inventory or non-household relationships, but I sometimes will re-save a household after kids are born or age up or a townie joins them.
When creating a new household, if you want to use a Sim you've previously created, go to "Open the Gallery" - the next icon over, which looks like a lightbulb.
When it opens, switch to the "My Library" tab
Choose the household you want to reuse and click "Place Household" in the bottom right corner.
You'll then have the option to merge (keep the existing Sim[s]) or replace (get rid of any Sims that were in the editor) to put a copy of the Sim you created previously into the new household.
Then you will have new copies of the previously created Sims, with editable traits
