Scenes and ensembles
One character can hold many storylines. An ensemble stage seats several of them in the same room.
Why one character holds many storylines
A storyline is a separate scene: its own title, opening, and chat. The character stays the same person.
When a scene needs more than one character
An ensemble stage puts two to five story cards in one room. A director chooses who speaks, and you can still nudge or narrate.