JIRA Software REST methods should use the same order as JIRA's for workflow transitions.
Agile boards don't respect the opsbar-sequence property. The REST method that retrieves available transitions - /rest/greenhopper/1.0/xboard/issue/transitions.json?issueId=<issue-id> - for the given issue follows no particular order.
The random order can be noticed on the "Update Parent Issue" dialog - which is triggered when all sub-tasks related to an issue have resolution set; and on the "Operations" dialog - that is called when clicking "More Actions..." in the context menu for issues in a board.
- Create a new Software project with a board, using the "Simplified Workflow";
- Check the current order for transitions on any of the situations outlined in Actual Behavior;
- Choose any two transitions from the workflow and set the opsbar-sequence property in a way the order is inverse to what is currently seen in the board;
- Publish the workflow with changes applied;
- Check that opening the issue through its direct link respects the order setup;
- Go back to the Agile board to check the order of transitions or access the afore-mentioned REST method;
- Notice the order of transitions is the same as on step 2, regardless of changes to the opsbar-sequence property.
There is no known workaround for this at the moment.