As far as I can tell, the only way to reorder feature priorities in in the features board view. It should also be available in features details for consistency.
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As described, the Feature board is the primary place to reorder feature priorities (allowing you to reorder features within and across releases).
The Feature Details page represents a more detailed look at a given feature and release. It offers different capabilities than the Feature Board page and allows the ability to sort features based on various criteria. At this time, we do not have plans to make updates in this area, based on current priorities and noted workarounds.