How can I get my Horizontal Scroll back to normal? It won't scroll to the left.
I can horizontally scroll to the right, but every time I try to go back to the left, a giant arrow appears and it jumps me to the last sheet I was using (in the same document, just a different tab)
What you are seeing if the web browser's "go back to previous page" feature. Google Sheets is not involved in what's happening.
You are most likely using a gesture like a two-finger swipe to the left. You can turn off that feature at > System Settings > Trackpad > More gestures > Swipe between pages.