Using extra mouse keys in X11
This procedure uses xev to identify extra mouse-button events, then binds those buttons through xbindkeys to xte commands that send keyboard shortcuts in X11.
Install required packages:
sudo pacman -Syu xbindkeys xorg-xev xdotool xautomation
Use xev to determine the events triggered by the mouse buttons.
Add to ~/.xbindkeysrc:
# Mouse Forward button
"xte 'keydown Super_L' 'key Page_Up' 'keyup Super_L'"
m:0x0 + b:8
# Mouse Back button
"xte 'keydown Super_L' 'key Page_Down' 'keyup Super_L'"
m:0x0 + b:9