Scroll direction on macOS is set for the system without taking into consideration whether a mouse or a trackpad is being used. You can change the scroll direction for macOS anytime you want from System Preferences but the direction will apply to both the trackpad and the mouse. There is no way to separate the two with just the OS settings. If you want to set a different scroll direction for the mouse and trackpad, you need a free app called Mos.
Different scroll direction for mouse and trackpad
Download and run Mos. It will need special accessibility permission to run. Once it’s running though, it will do so with the option to reverse the scroll direction for the mouse wheel. You don’t need to set it up, and you don’t need to have a mouse connected to your system either. Any time you do connect a mouse though, its wheel will scroll in the opposite direction than that of the trackpad’s scroll gesture.
Mos also has one other, really neat feature. It lets you add exceptions for the scroll direction on a per-app basis. Go to the app’s preferences and select the ‘Exception’ tab. Click the plus button at the bottom and select an application. If you want the scroll direction of the mouse to be reversed in the application, leave it as is. If not, uncheck the Reverse box for the application and the scroll direction will not be reversed.
Finally, you can also manage the scrolling smoothness with Mos. Go to the Advanced tab and tinker with the three sliders there; Step, Speed, and Duration. The Step sets the minimum scroll distance i.e., how ‘far’ or how many ‘lines’ are scrolled. The Speed has to do with smoothness and how ‘fast’ the scrolling appears to be. Duration is for the scroll animation and while it’s purely a cosmetic change, it may effect how fast the scrolling appears.
Mos has features that you’d expect macOS to have by default. If nothing else, there should be a way to set different scroll directions for the mouse and the trackpad.
Mos won’t run at login by default but it has a built-in option that allows you to add it to the login items. It also offers stats on how ‘far’ you’ve scrolled and it lets you set a hotkey that allows you to change the scroll direction. The app is like steroids for an average mouse. If you use a mouse with your MacBook, this app is hard to live without.
Need to disable the trackpad when you connect a mouse? There’s a way to do that as well.