With Synaptics, use xclient in terminal to adjust. No reasonable gui exists to match that. Run 'xclient -l' to see current. Then new values are tested from cli with key=value pairs. When you find what you like, then you put in a config file.
I am not running Synaptics anymore, but I there is a template config under /usr/share/synaptics/X11 (or similar). You copy that to /etc/X11/xorg.conf.d. Then put in your settings.
If you have trouble finding that config file, get a file list from the Synaptics package (dpkg -l synaptics). If you get stuck, while back here and I will get a link for you.