DFS 10.4.0 - Asset metadata viewer
With the metadata viewer, you can inspect data from the 2 indexes dfs_assets_master_index and dfs_assets_web_index. Enter an assetId and select the language to lookup. It will fetch all the metadata around an asset and do a comparison between master and web. This will tell you if the data is not in sync on the web.
If you know that an asset for some reason has not been synchronized into Sitecore, you can enter the assetId and click the button Sync asset from Digizuite. This will synchronize the asset into Sitecore, update the metadata, or create a new item if it did not already exist in Sitecore.
Media preview shows the different qualities of an asset. Out of the box, it only shows previews from CM. You can add your CD servers to the configuration parameter DFS.Administration.contentDelivery.baseUrls in App_Config\Include\damforsitecore\DFS.Settings.config. This is useful when you want to verify that an image is the same on both the CM and CD server. If you, for example, replace an asset in Digizuite and then never publish your changes, the image on CM and CD will be different if it is cached on CD.