Extended metadata (XMD) enables you to customize the formatting of dashboard elements in Wave Analytics. To know the in-depth details about the configuring options, refer to the official documentation (https://developer.salesforce.com/docs/atlas.en-us.bi_dev_guide_xmd.meta/bi_dev_guide_xmd/bi_xmd_intro.htm).

In order to access the XMD of the dashboard, navigate to the dashboard and use CMD + E (on macOS). The extended metadata of the dashboard can be viewed. You can edit the XMD to format measures, change labels, color-specific fields, and generate links to the Salesforce organization. The extended metadata for the dashboard is shown in the following screenshot: