Although you can set the outbound rules on an AKS Load Balancer, this is not a best practice. Outbound rules & Public IPs are designed to be controlled and managed by AKS. Future AKS upgrades will have the same effect on your outbound rules if you continue to do it this way.
The best way to do this in AKS is to configure your cluster to use multiple LB IPs, and it requires a simple 'az aks update' command using the '--load-balancer-managed-outbound-ip-count' flag as described in the doc. Each additional IP address provided by a frontend provides 64k ephemeral ports for Load Balancer to use as SNAT ports. Changes done this way will persist through version upgrades.