A bit of googling suggests that (historically at least, possibly still true) there isn't a built-in way, but you could with an addon. Most likely an addon can

A bit of googling suggests that (historically at least, possibly still true) there isn't a built-in way, but you could with an addon. Most likely an addon can still do this - detect tab-open and convert to window-open ¯\_(ツ)_/¯ I don't have any implementations I can point to, though. And a brief browse of about:config didn't yield anything interesting.