Improve "Step size" control.

[ninbura]

Currently "Step size" control is a bit lacking.

1. There's no method of specifying a specific number of lines.
   • If I want to match the step size on multiple Macs, I have to match them visually. The ability to specify an exact number of lines would be appreciated.
2. The slider/control does not provide a high level of granularity.
   • When I increase the slider by its smallest increment, there is no change to step size in reality. Eventually if you move the slider enough, a change is propagated, but that change is larger than I want. It'd be much more desirable if the control was more granular, and allowed for increments of 1.

Alternative applications seem to have better control over step size. However, I'm in a weird situation where I need to disable natural scrolling in macOS, and then reverse the trackpad scroll direction. It seems only your app is capable of reversing the trackpad when compared to alternatives.