While I think this should work the delete button in multi message view exactly as for that in message header view (and is easy to fix), I am not so sure about the "Delete selected messages" item under the menu bar. Does anyone really use that workflow? Anyway, to fix it there as well appears to be much more complicated, since the exact menu item is used for other delete tasks (such as folders) as well.
Bug 1913401 Comment 2 Edit History
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While I think this should work for the delete button in multi message view exactly as for that in message header view (and is easy to fix), I am not so sure about the "Delete selected messages" item under the menu bar. Does anyone really use that workflow? Anyway, to fix it there as well appears to be much more complicated, since the exact menu item is used for other delete tasks (such as folders) as well.