https://wiki.archlinux.org/index.php/Mouse_buttons
install xbindkeys
vi ~/.xbindkeysrcxbindkeys
# too much echo#"xvkbd -text "\[Return]""# m:0x0 + b:11"xte 'keydown Return' 'keyup Return'" b:12
# b:11
Create or edit your portal override config at ~/.config/xdg-desktop-portal/niri-portals.conf (or globally at /usr/share/xdg-desktop-porta...
