@Smart-Communities the red on the Short Bookmarks page is not showing the online/offline status of the computer. It's telling you that the command/computer combo no longer exists.
For example, I have a command on my DS computer that no longer exists. I probably renamed it.
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If you click Configure, it will show you a blank Select Trigger field with a pulldown to re-select something for that short bookmark URL.
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About your other questions:
Q: Possible to display short bookmarks on the main " View Triggers" screen?
A: It's currently not possible. How about I move the "Create Short Bookmark" button to the top of the Bookmark page?
Q: Create shorter bookmarks by default?
A: I think there's a legit use case for the original bookmarks. They're meant to be ephemeral - they can expire after a set number of hours. They're also invalidated if the command is deleted or renamed. Short bookmarks are valid as long as the computer name and command name they refer to exist.
Q: If I delete offline devices will they come back if eventually online again?
A: No, so if you delete a computer, you'll need to re-input a token when the agent runs on it again, and it will create a new computer record for it at that point.