If I want to use two windows to edit an email, I would use two windows to edit email. This is their desktop browser interface. If I want to pop out my compose

If I want to use two windows to edit an email, I would use two windows to edit email. This is their desktop browser interface. If I want to pop out my compose window from the browser, I can drag the tab out from the browser myself. Doing that kind of thing automatically through haphazard invented interface schemes makes browsing the web on the desktop a worse experience.