Daniel told me how to set up scroll wheel emulation on a Thinkpad. Presumably it works on other systems as well, but the magic numbers for xinput may be different. I wrote a script to set it up, and configure my GNOME session to run it upon login.

The result: pressing the middle mouse button and moving the trackpoint up/down or left/right results in the applications receiving events as if a scroll wheel had been used.

Very, very handy. Thanks, Daniel.

#!/bin/sh

set -eu

id=$(xinput list | sed -n '/TPPS\/2 IBM TrackPoint/s/.*id=\([0-9]\+\).*/\1/p')
emu=$(xinput list-props "$id" | 
    sed -n '/Evdev Wheel Emulation (/s/.*(\([0-9]\+\)).*/\1/p')
but=$(xinput list-props "$id" | 
    sed -n '/Evdev Wheel Emulation Button (/s/.*(\([0-9]\+\)).*/\1/p')
axs=$(xinput list-props "$id" | 
    sed -n '/Evdev Wheel Emulation Axes (/s/.*(\([0-9]\+\)).*/\1/p')
xinput set-int-prop "$id" "$emu" 8 1
xinput set-int-prop "$id" "$but" 8 2
#xinput set-int-prop "$id" "$axs" 8 6 7 4 5