Just stumbled upon it myself. It turns out that the requirements-based test suite is a special case of the query-based suite, which also cannot be ordered. All test cases related to the requirements / user history will be shown in the corresponding test suite.
As for bypassing the default sort order (apparently, the id of the test case work item), I could not find it. However, you can approximate a requirements-based query using a regular query, and then use the ability to sort packages based on queries. There are two problems with this: (1) the requirements associated with the test case are not available in the query editor, so you will have to use some other criteria; and (2) you still do not have a special test case order dispatcher, as is the case with a test suite without a request.
I did not find anything about adding ordering to test suites based on requirements in the upcoming version or in any third-party tool. Maybe something to see in the making.
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