Samsung Galaxy Note 4 - Manual (Page 59)

Motions & usability features
59
Launching Multi window from the list of recent apps
1
Tap .
2
Swipe upwards or downwards and tap to launch an app in Multi window.
3
Select another app to launch in Multi window.
Using Multi window options
When you use Multi window apps, select an app window and tap the circle between the app
windows to access the following options: