I use milestones, for that. I almost never set a "due date". I find the milestone feature useful for doing, well, lot of not milestone related things.

First, they have a three columns (unstarted / started / completed) which adds easily simple trello-like boards to your projects.

Then, issues in those columns are sortable, like you describe, to prioritize. Simple drag'n'drop, could not get easier.

And finally, I use their description as a "release note". When MRs mention tasks to run on deploy, I'll just add them in milestone description, and I'll have a central doc for release.