Change mouse primary key in setting in i3WM XFCE

General system Newbie
3

What if you insert this line into i3 config:

# Autostart apps as you like
exec --no-startup-id xmodmap -e "pointer = 3 2 1"

Edit1: If you insist on a GUI setting consider merging XFCE and i3 (Then: Settings Manager / Mouse and Touchpad)
It still works