When creating a new item, if one creates that job as a copy of an existing branch, the resulting job is not editable or deletable. There is no way that I can see to edit or delete the newly created job.
The reason one might want to do this is to turn a given branch build into a recurring task. What I thought was the obvious solution was to create a new item coped from the existing one, with the intention of adding in a schedule trigger.
Ideally, this would just work, but as a stop-gap it should probably have been prevented from happening in the first place by filtering out such immutable/generated jobs as copy-from candidates.