Apple menu > System Preferences > General
Show scroll bars
Scroll bars appear in a window when there’s content that doesn’t fit into the window’s current size.
Automatically based on mouse or trackpad: Scroll bars are shown depending on the mouse or trackpad you’re using.
If your device allows gestures, scroll bars are hidden until you start scrolling. Otherwise, they’re visible.
When scrolling: Hide scroll bars until you start scrolling.
Always: Scroll bars are always shown.
Click in the scroll bar to
Jump to the next page: Clicking in the scroll bar moves the content page by page.
Jump to the spot that’s clicked: Moves to the spot where you’re clicking; for example, if you click at the bottom of the scroll bar, you go to the bottom of the document.
To momentarily switch between scrolling methods while working, press and hold the Option key while clicking the scroll bar.
