Completed releases don't show in the started roadmap so why would abandoned releases? They are adding noise to our display, annoyingly so where we are considering marking them as "shipped" to remove them from various lists.
Thank you for your idea. It is currently possible to remove a release from the starter roadmap. You can click the more options icon on the right side of the release bar and select Remove from roadmap.
So the admin comment describes removing it from the roadmap but doesn't remove it from the listable options of releases one can add. It's awkward that shipped releases don't show up in the list but abandoned releases do.