Once the chicken is easily shreddable, remove from the slow cooker and shred using two forks. Place back into the slow cooker and let the shredded chicken absorb the BBQ juices.
In a large bowl, combine the red onion, carrots, shredded cabbage, ranch dressing, and minced jalapenos if using. Mix well, then use immediately or store in an airtight container in the fridge for up to 5 days.