Story Mode was added to Sims 4 with Patch 1.53.115 and lets you create a Sim by answering some basic questions.
Sims created this way already have an aspiration, traits, a job, some skills and a fixed starting fund.
The look as well as name/gender/voice/walking style can then be adjusted to whatever you like. You won’t be able to change the achievement, traits or the starting bonuses. Those are all based on the answers you gave to the questions.
After creating one Sim, you might want to create another in the same household also in story mode. You can do this as always by clicking on the +Sim Icon and then choosing the option Add Sim via a Story. This will trigger the questions.
If you create a Sim on an existing save either through the household manager or the button in the world map, the story mode isn’t triggered automatically. The question if you want to create a Sim in that mode doesn’t pop-up even for new households.
To create a Sim in story mode follow the same steps as adding another Sim to a household through the +Sim Icon. Just delete the first Sim after adding a second one if you don’t want to keep that Sim.
If you upload a Sim created in story mode to the gallery/library the story icon as well as the starting funds aren’t saved with the Sim as that isn’t information the gallery knows about.
If you download such a Sim, he will have the skills and the job like every other Sim uploaded but no knowledge that he was created through Story Mode.
The story icon is only retained until you place the Sim into a game. Taking him to CAS afterwards doesn’t show the story icon anymore.