[HSY] How to change active lot type in Auditorium venue through build mode

How do I change the active sub-lot type (Auditorium, formal dance, graduation day, career day)  to make it ACTIVE. I know how to change between each one, but how do I make it the current active lot. The problem is I last edited career day lot, and switched back to auditorium, but the game keeps marking the career day lot as active. Through the world map, it marks it as the career day auditorium. the big problem is if I travel there with my sim through a regular basis (no events), it will still treat career day as default since it was the active one.