Add Adv Config (#451)

* Add Adv Config

* Update central-configuration.md

Author: theletterf

docs/reference/central-configuration.md

@@ -13,7 +13,7 @@ products:
 
 # Central configuration for EDOT SDKs
 
-Manage {{edot}} (EDOT) SDKs through the APM Agent Central Configuration feature in the Applications UI. Changes are automatically propagated to the deployed [EDOT SDKs](/reference/edot-sdks/index.md). Refer to [APM Agent Central Configuration](docs-content://solutions/observability/apm/apm-agent-central-configuration.md) for more information.
+Manage {{edot}} (EDOT) SDKs through the APM Agent Central Configuration feature in the Applications UI. Changes are automatically propagated to the deployed EDOT SDKs. Refer to [APM Agent Central Configuration](docs-content://solutions/observability/apm/apm-agent-central-configuration.md) for more information.
 
 This feature implements the Open Agent Management Protocol (OpAMP). Refer to [Open Agent Management Protocol
 ](https://opentelemetry.io/docs/specs/opamp/) for more information.
@@ -24,7 +24,7 @@ To use APM Agent Central Configuration for EDOT SDKs, you need:
 
 * An Elastic self-managed or {{ecloud}} deployment, version 9.1 or higher.
 * A standalone [EDOT Collector](elastic-agent://reference/edot-collector/index.md), in either Agent or Collector mode.
-* [EDOT SDKs](/reference/edot-sdks/index.md) instrumenting your application.
+* EDOT SDKs instrumenting your application.
 
 The following versions of EDOT and {{stack}} support central configuration:
 
@@ -140,12 +140,22 @@ Your application must produce and send telemetry data for the EDOT SDK to appear
 For a list of settings that you can configure through APM Agent Central Configuration, refer to the configuration reference of each EDOT SDK:
 
 - [EDOT Android](apm-agent-android://reference/edot-android/configuration.md#central-configuration)
+- [EDOT iOS](apm-agent-ios://reference/edot-ios/configuration.md)
 - [EDOT Java](elastic-otel-java://reference/edot-java/configuration.md#central-configuration)
 - [EDOT Node.js](elastic-otel-node://reference/edot-node/configuration.md#central-configuration)
 - [EDOT PHP](elastic-otel-php://reference/edot-php/configuration.md#central-configuration)
 - [EDOT Python](elastic-otel-python://reference/edot-python/configuration.md#central-configuration)
 
-EDOT iOS currently supports APM Agent Central Configuration through APM Server. Refer to [EDOT iOS configuration](apm-agent-ios://reference/configuration.md) for more details.
+## Advanced configuration
+```{applies_to}
+stack: preview 9.2
+```
+
+The **Advanced Configuration** feature allows you to define custom configuration options as key-value pairs. Settings are passed directly to your EDOT SDK.
+
+:::{warning}
+Use this feature with caution. An incorrect or incompatible setting might affect the behavior of the Collector.
+:::
 
 ## Deactivate central configuration