If the change is to a Kubernetes field (such as modifying a Deployment attribute), it will likely need to be install-time configuration.
However, that doesn't necessarily mean a PR to add a value will be accepted.
The `values.yaml` API is intended to maintain a *minimal core set of configuration* that most users will use.

message ExtraValue {
  // items, if empty, will result in an empty slice

  repeated string items = 1;
}

// SelfSubjectReview contains the user information that the kube-apiserver has about the user making this request.
// When using impersonation, users will receive the user info of the user being impersonated.  If impersonation or
// request header authentication is used, any extra keys will have their case ignored and returned as lowercase.

  // and notAfter fields in the issued certificate to determine the actual duration.
  //
  // The v1.22+ in-tree implementations of the well-known Kubernetes signers will
  // honor this field as long as the requested duration is not greater than the
  // maximum duration they will honor per the --cluster-signing-duration CLI
  // flag to the Kubernetes controller manager.
  //
  // Certificate signers may not honor this field for various reasons:

  // MutatingAdmissionWebhook and ValidatingAdmissionWebhook admission controller will prefix the keys with
  // admission webhook name (e.g. imagepolicy.example.com/error=image-blacklisted). AuditAnnotations will be provided by
  // the admission webhook to add additional context to the audit log for this request.
  // +optional
  map<string, string> auditAnnotations = 6;

    ports:
    ## You can add custom gateway ports in user values overrides, but it must include those ports since helm replaces.
    # Note that AWS ELB will by default perform health checks on the first port
    # on this list. Setting this to the health check port will ensure that health
    # checks always work. https://github.com/istio/istio/issues/12503
    - port: 15021
      targetPort: 15021
      name: status-port

  // implementation will use to handle pods of this class. The possible values
  // are specific to the node & CRI configuration.  It is assumed that all
  // handlers are available on every node, and handlers of the same name are
  // equivalent on every node.
  // For example, a handler called "runc" might specify that the runc OCI
  // runtime (using native Linux containers) will be used to run the containers
  // in a pod.

# retry.sh retries a command until it succeeds. It accepts a regex pattern to match failures on to
# determine if a retry should be attempted.
# Example: retry.sh "connection timed out" ./my-flaky-script.sh some args
# This will run "my-flaky-script.sh", retrying any failed runs that output "connection timed out" up
# to 5 times.

function fail {
  echo "${1}" >&2
  exit 1
}

function isatty() {
 if [ -t 1 ] ; then
   return 0

	// The HTTP port for monitoring
	MonitoringPort int

	// The UDS server address that CNI plugin will send log to.
	LogUDSAddress string

	// The watch server socket address that CNI plugin will forward CNI events to.
	CNIEventAddress string

	// The ztunnel server socket address that the ztunnel will connect to.
	ZtunnelUDSAddress string

	// Whether ambient is enabled
	AmbientEnabled bool

# Stability, security, and performance are not guaranteed - use at your own risk.
meshConfig:
  defaultConfig:
    proxyMetadata:
      # Enable Istio agent to handle DNS requests for known hosts
      # Unknown hosts will automatically be resolved using upstream dns servers in resolv.conf

# Stability, security, and performance are not guaranteed - use at your own risk.
meshConfig:
  defaultConfig:
    proxyMetadata:
      # Enable Istio agent to handle DNS requests for known hosts
      # Unknown hosts will automatically be resolved using upstream dns servers in resolv.conf