Request help to add a custom link before search icon on the AEM header as show in the below image. On click of the custom link we just want to open some other http url. We want to show this link to only one specific tenant. Any suggestion will be great of help. Thanking you. link
In order to customize or extend the AEM OOB functionality, one needs to overlay in AEM.
In AEM 6.4 version, I have found that the black background header is generated from the location /libs/granite/ui/content/shell/header/actions and noticed that it's marked as granite:internalArea as mixin type.
Following Adobe documentation it says that "Internal (granite:InternalArea) - Defines a node as internal. Nodes classified as internal cannot be overlaid, inherited, or used directly. These nodes are meant only for internal functionality of AEM" . This means that you should not modify areas that your product vendor has marked as InternalArea. This has been done to ease Upgrade for your client, this path should not be overlaid.
But if you want then you could simply remove the mixin via CRX/De interface, see Mixin button. Then you can overlay /libs/granite/ui/content/shell/header/actions and add your custom functionality but this is not recommended.