If you already have a rabbitmq secret, you can use that instead with TriggerAuthentication rather than provide the values via .spec.env. You can do that by using secretTargetRef.
apiVersion: keda.sh/v1alpha1
kind: TriggerAuthentication
metadata:
name: rabbitmq
namespace: keda-demo
spec:
secretTargetRef:
- key: management-uri
name: rabbitmq
parameter: host
apiVersion: v1
data:
amqp-uri: redacted
management-uri: redacted
kind: Secret
metadata:
name: rabbitmq
namespace: keda-demo
type: Opaque
Reference: https://keda.sh/docs/2.20/scalers/rabbitmq-queue/#authentication-parameters