I found this on the apple website, as it seems that the default scroll bar setting is to auto-hide. The only way to manually make it scroll is to drag left/right while selecting text. Try changing the Mac defaults (effects TT immediately).
from https://discussions.apple.com/thread/[removed]?sortBy=rank
From the Apple menu, select System Settings. Click Appearance. The following screen displays. Set the Show Scroll Bars setting to Always.
Similar, but with screenshots - https://support.wix.com/en/article/mac-users-unable-to-see-scroll-bar-in-the-editor
