I am using a MacBook Pro with Big Sur. Unfortunately I cannot see a (vertical) scroll bar in my R script that is opened in the source pane, which would be very helpful for long scripts.
I have found several topics related to this issue, but no conclusive answer on how to fix it.
Do you see the scrollbar when you are actively scrolling? There's a setting in macOS that controls when scrollbars appear; you might need to set it to "always" if you don't want the scrollbar hidden.