Hey, @Aravisian ! That's so close to what I wanted.
What happens now is that I have to HOLD the scroll click and move up and down as if it was scrolling a scroll bar. The pointer freezes and the content moves; it doesn't continuously move toward the direct I point.
I'm not too good at Linux, but I was reading libinput documentation for Arch Linux and there's a section that says:
Scroll with mouse by holding a button
There is a nice trick to optimize scrolling with a mouse or trackball by holding a mouse button (like right or middle button, or some other if the mouse has more buttons) and moving the mouse. Very useful in case your mouse does not have the mouse wheel (often the case with the trackballs). To do that one has to set ScrollMethod to button and specify the mouse button in the ScrollButton option for the action. Here is an example for configuration to achieve that:
Option "ScrollMethod" "button"
Option "ScrollButton" "3"
It obviously doesn't work the same because it's not the same distro (it mentions "Xorg" for this config), but would it give any idea on how to set this for libinput?