This article explains how to configure scroll bars on a Mac running OS X Lion or later versions of OS X and macOS. Set preferences to always show scroll bars, and control the scrolling speed of your mouse or trackpad.
How to Always Show the Scroll Bar on Your MacBook [Tutorial]
You can adjust the sliders to your liking.
From the Apple menu, select System Preferences.
In the System Preferences window, select the General icon in the upper-left corner.
