Add notes about the branding system setting

Relates to: harvester/harvester#6331

Signed-off-by: Volker Theile <vtheile@suse.com>

docs/advanced/settings.md

@@ -562,6 +562,13 @@ When the node becomes unavailable or is powered off, the VM only restarts and do
 
 **Default value**: **Harvester**
 
+:::caution
+
+This setting is part of the `settings.management.cattle.io` custom resource.
+Because of that you can't configure this setting, including `Logo`, `Favicon`, `Primary Color` and `Link Color`, using a [Harvester configuration](../install/harvester-configuration.md#system_settings) file.
+
+:::
+
 ![containerd-registry](/img/v1.2/advanced/branding.png)
 
 **Supported options and values**: