Android studio before 2.2 version at the xml design screen there was a view like \"Preview all screen sizes\" (check the image) but I cannot find that in Android Studio 2.2 Bet
While preview all screen sizes seems to be gone, it is possible in 2.3 to view more than one screen size at the same time.
Right-click on the activity_main.xml (or whichever xml file) tab, and from the pop-up menu select split-vertically or split-horizontally.
This will create a second xml tab that can use a different screen for design/text. This can be repeated for more tabs, and the tabs can be "torn off" to float separately.