Provide external yaml file to JCasC configScripts

I am configuring my Jenkins instance using jenkins-helm chart (https://github.com/jenkinsci/helm-charts/blob/main/charts/jenkins/VALUES_SUMMARY.md#jenkins-configuration-as-code-jcasc)

Currently Jenkins config is provided in values.yaml as:

jenkins:
  controller:
    JCasC:
      configScripts:
        key1:|-
          <a-very-big-yaml-value>

Is there a way to import this 'big-yaml-value' from separate yaml file, as it will enhance maintainability of code for us.

Based on previous answers, Here is an example how I made it work with multiple configuration yaml files to load into JCasC, using terraform:

Jenkins module folder:
-- configs
   - kubernetes.yaml
   - default-config.yaml
   ...
-- main.tf
-- values.yaml

values.yaml:

   controller:
      JCasC:          
        defaultConfig: false
      persistence:
        enabled: true
        existingClaim: efs-claim-jenkins
      volumes:
        - name: jenkins-custom-casc-config
          configMap:
            name: jenkins-custom-casc-config
      mounts:
        - mountPath: /var/jenkins_home/casc_configs/custom
          name: jenkins-custom-casc-config
          readOnly: true

main.tf:

resource "kubernetes_config_map" "jenkins-custom-casc-config" {
  metadata {
    name      = "jenkins-custom-casc-config"
    namespace = "jenkins"
  }

  data = {
    for file in local.config_files :
    basename(file) => file("${path.module}/configs/${file}")
  }
}