M720 mouse has quite a few buttons. But remapping them under Linux is not necessarily the easiest thing in the world. For example, if one wants Forward and Backward buttons remapped to window left/right snap, there are a few things that need to be done manually.
First we need a few packages:
sudo apt install -y xbindkeys xautomation
Then we need to figure out which code our forward and backward keys are:
xev | grep -A 2 Button
In my case, these were 8 and 9 respectively.
Then we need to write mappings in
"xte 'keydown Super_L' 'key Left' 'keyup Super_L'"
"xte 'keydown Super_L' 'key Right' 'keyup Super_L'"
And lastly, we need to restart xbindkeys:
killall xbindkeys 2>/dev/null
If all went well, your buttons now know a new trick.