I fully agree with Douwe: "We used to have an option for "Backlog" in the milestone dropdown as a virtual milestone containing all issues without a milestone. It's gone as of 7.11, and I think we should restore it, but probably not in a patch release. (edited)"
@kaystrobach Regressions are things that worked in the previous release, but were broken in the next, i.e. something that worked in 7.11 but no longer did in 7.12. Issues like that warrant an expedited release in the form of a 7.12.x patch release.
Since this feature already went missing with 7.11, it is not a regression from the perspective of 7.12, so we're categorizing it as a regular issue.