For some reason the only three finger swipe gesture that shows up in the Synaptics driver is for switching apps.
I want three finger swipe to be forward and back in browsers.

I found the following instructions:

Open Regedit and Navigate to:
HKEY_CURRENT_USER
SOFTWARE
Synatics
SynTP
Touchpadxxxxx
3FingerGestures

For making back and forward swiping work in browsers:
ActionID1 = 5c
ActionID3 = 1c
ActionID5 = 5d
ActionID7 = 1c

Reboot.  The driver will still show “Switching Apps” as the three finger gesture but it forward and back start working.