As an organization you may have added admins to manage content and permissions in Microsoft Stream.
This article explains what capabilities exist for a Microsoft Stream admin and walks you through the steps and experiences for the various personas.
You need to be a Microsoft Stream Admin to perform this operation. For more information, see this article.
If you are a Microsoft Stream Admin, you will see the Edit in admin mode menu item for all videos (even if you are not the owner of that video) as shown in the following image.
You can also select this item from the playback page for organizational videos.
Once you click Edit in admin mode you will have elevated permissions for that video and will be able to edit all metadata for that particular video such as updating description, updating the thumbnail for the video.
After you have made your changes to the video metadata, you can click Apply changes and exit, which will take you to the video playback page with the updated metadata. However, if you click Cancel and exit, you will still land in the video playback page, but your changes will not be saved. If you want to make changes to this video at a later point, you will need to Edit in admin mode again.
Let's say someone from your organization shared a URL to the video playback page that has custom permission set and you are not a part of the original users for whom the video was intended. As an administrator, when you click that video link, you will see the following screen:
You notice that the system has already identified you as a Microsoft Stream admin, and therefore it shows the burgundy color warning that this video can only be accessed in admin mode. You can now choose to View in admin mode, which elevates you to view the video and make any changes in admin mode.
Once you click View in admin mode, you will land on the playback page for that custom video with the burgundy color warning indicating that you are accessing this private/custom video in admin mode.
If you decide to make changes to the metadata of this custom video, you can click the Edit in admin mode in the drawer and that will lead you to the edit page for that particular video.
If you apply changes, it will save your changes and exit you out of admin mode and land you on the original video playback page.