For some reason the button that makes a list of functions appear in the left hand column has disappeared. I’m left with the buttons for collaboration, databases, open files, and locations:
I think you mean View menu > Tabs & Sidebars > Code. You may have reset your profile recently which would put the code browser into it’s default position in the right pane.
Thank you, @careyh and @nathanr! For some reason the code browser had moved to the right pane, which I never have open; I’ve now moved it back to the left pane