Thinkpad middle button config
Step 1. Create a new file

sudo nano /usr/lib/X11/xorg.conf.d/20-thinkpad.conf

Step 2. Insert the following

Section "InputClass"
Identifier "Trackpoint Wheel Emulation"
MatchProduct "TPPS/2 IBM TrackPoint|DualPoint Stick|Synaptics Inc. Composite TouchPad / TrackPoint"
MatchDevicePath "/dev/input/event*"
Option "EmulateWheel" "true"
Option "EmulateWheelButton" "2"
Option "Emulate3Buttons" "false"
Option "XAxisMapping" "6 7"
Option "YAxisMapping" "4 5"
EndSection

Step 3. Save file, restart computer, and enjoy!