Block editor sections appear in sidebar

I am using the latest WordPress update. I am using the block editor. I created several pages adding sections and items. That all worked well until I clicked the up arrow next to the title section at the top of the page. Now all the sections have been moved to the sidebar on the right side of the screen. I cannot find any way to undo this so the sections, etc. appear in the main editing part of the screen.

Can anyone point me to a way to fix this?