Ok I give up, I have no idea how to do the command line switch on macos
https://superuser.com/questions/3585...dows-shortcuts
This says it might be possible, but idk how.
I found inside the contents of the epub-viewer application inside the calibre application, there's a unix executable file that will launch a new instance/window of the viewer, but it is tied to a command line interface. That is not exactly ideal.
If anyone knows how to trigger a new window of the viewer on macos when opening a epub let me know, thanks.