Ok I understand that, but that is not my concern (and perhaps not the OP's). Let's be clear here, I think the post's title, "not displayed on Windows", and the post's text refers to Microsoft Windows, NOT windows as in Vivaldi's realm. Perhaps it should've been clearer (by saying MS Windows and version number) but to me it was obvious he meant MS Windows because of the capital W and the later text mentioning the Task Bar and Task View features which are found in Windows (versions 10 & 11 at least). That's why I think you are missing the point and why I say Off Topic, sorry if I offended you but this is a simple misunderstanding.
Now on topic, there's no way to name the windows (as in Chromiums right now) so that it will show up in Microsoft Windows' Task View and Task Bar ? If so, I'd really make the display of at least the workspace name in there a priority, so that it becomes accessible outside of Vivaldi.