Yes but unfortunately that doesn't really work for heavy applications today. That would mean like 50 independent memory-hungry firefox or IDE processes corresponding to every tab/file you might have open. The entire point is to decouple a window from the resources/host process that controls the window.
Why would an IDE have a separate process for another window? At least, Idea does it right (iirc).
As for FF, I have 47 windows opened, but 11 processes running—one of which is a ‘master’ process. Meanwhile tabs that are in one window can still run in multiple processes.
multiple browser windows are not different resource-wise than multiple tabs, you are still running against same instance of the browser.
The other benefit of leaving window (and tab) managerment to the OS is that tabs switching should also better, imagine your tabs show up in the OS switcher and you can look them up in spotlight or something.
FF might have a setting on ‘about:config’ for whether to open links in tabs or windows. But off-hand I only know for certain about the one for links from other apps.
