TeXstudio Keep two pdf views of the same tex file
I would like to point out that the SumatraPDF viewer does not lock the pdf file. This means that you can keep your pdf file open when you recompile it.
Furthermore, it provides an inverse search, meaning that you can double-click on your pdf file and it will open your tex file (even on the position).
I dont know about the other viewers, but on Linux, the 'document-viewer' of Debian doesn't lock the file and auto-updates the view when the file is changed.
Update: Okular reloads the file too.
TeXstudio can have dozens of viewing windows (though I guess about 5 would be more than enough), so unclear as to reason for the question. Here is a dual screen shot with only two open. In addition from ANY of them you can open another external viewer. Here I show SumatraPDF as a lightweight example but it could have been Edge or any PDF handler such as evince Okular etc. Just add your choice to the Options Configure Commands External PDF viewer (simply point it at your executable) then you simply hit the red book Icon in the window you want duplicated.
If you do not want the additional windows to track the same editing position you need to (in that secondary window) toggle Configure > Ignore for synchronisation.
It gets a little more complicated for twin editing windows but the system is basically the same, even if a bit confusing.
For other ways to run dual compile using split editor and viewers see
https://tex.stackexchange.com/a/473233/170109 (dual sessions/instances)
https://tex.stackexchange.com/a/472480/170109 (split editor) and
https://tex.stackexchange.com/a/472806/170109 (split editor and viewers)