i found this in /etc/X11/xorg.conf.d
to help
Section "InputClass"
Identifier "touchpad overrides"
Driver "libinput"
MatchIsTouchpad "on"
Option "Tapping" "off"
Option "ClickMethod" "clickfinger"
Option "NaturalScrolling" "false"
#Option "ScrollMethod" "edge"
EndSection
this was after updating packages on my chromebook. Synaptics was way too buggy with xorg 1.20.7 (or newer)
but if your synaptics is working just fine and you are not using libinput yet I wouldnt set this. I think the tap buttons of synaptics is phase out now. and i was really use to it but i couldnt at all adjut any of functions of source code