Re: please tell users right way to undo inside query-replace

[Richard Stallman]

    But it doesn't mention how to even one little undo.

    One little undo [C-/] is all it takes to break a, say,
    dired-do-query-replace-regexp or other long and involved job.

The doc string says,

    If you exit (\\[keyboard-quit], RET or q), you can resume the query replace
    with the command \\[tags-loop-continue]."

Did you try that?  Did it work?