Samsung Galaxy Note 4 - Manual (Page 63)

Motions & usability features
63
One-handed operation
An introduction
You can switch to one-handed operation mode to conveniently operate the device with one
hand.
On the All apps screen, tap Settings
→ Display and wallpaper → One-handed operation.
Reducing the screen size
Tap Reduce screen size and tap the Reduce screen size switch to activate it.
To switch to one-handed operation mode, hold the device in one hand. Then, quickly drag
your thumb from the edge of the screen to the centre of the screen and back again.