The Quartz Window Manager adds to the Windows menu all NSWindows with
titles. Since we assign a default title to all windows that produced a
rather cluttered Windows menu containing among other things dialogs.
Setting aside that dialogs don't belong in the Windows menu, if
a dialog was hidden for reuse instead of destroyed it would persist in
the Windows menu and if clicked there would show, but because it wasn't
running wouldn't respond to events and so couldn't be hidden again and
would remain on top of its parent window.
Ref: https://bugs.gnucash.org/show_bug.cgi?id=797807
c884308da3