viking-test-app chart supports custom VCL.

charts/viking-test-app/templates/varnishconfig.yaml

-{{ if .Values.acls -}}
+{{ if or .Values.acls .Values.vcl -}}
 {{ if empty .Values.vikingAdmSvc -}}
   {{ fail "Viking admin Service must be specified" -}}
 {{ end -}}
@@ -18,4 +18,8 @@ spec:
   acl:
     {{ toYaml .Values.acls | nindent 4 }}
   {{- end }}
+  {{- if .Values.vcl }}
+  vcl: |
+    {{ .Values.vcl | nindent 4 }}
+  {{- end }}
 {{- end }}

charts/viking-test-app/values.yaml

@@ -40,3 +40,6 @@ vikingAdmSvc: ""
 
 # ACL elements for VarnishConfig
 acls: []
+
+# If non-empty, include as-is as custom VCL.
+vcl: ""