Editing non-trivial variables in debugger view has no effect (cdb)

https://wiki.qt.io/Qt_Creator_ManualTests_DebuggerCdb says:

Stop at a breakpoint with one initialized QString, std::string and char[]. Can you edit their contents in "Locals and Expressions" view? Will the program continue with these changed values?

Editing a QString does not seem to have any effect: The contents are reverted to the old value immediately. (It does seem to work for int variables, by the way.) I can see how this functionality might be of the "fragile" kind, but then it should probably not be in the list of things to test.