What's your question
How do I stop a scan that's currently running?
Bob's images clearly shows the Stop Scan, but you go on to say "This is what appears when I click Custom Scan." That isn't going to Stop the Scan, I just started a Smart Scan and shortly after that clicked the Stop Scan and it stopped it..
If you can't actually see the Smart Scan running screen of his image, if you minimised/closed the scan window, then try looking at the avast tray icon it should be animated. I hovered over that and it showed a small toaster screen with the Smart Scan running, when it completed it then allows you to see the details.
Edit: if the scan is still running there should be a Stop Scan button in the window.
A video isn't really necessary, a still of the screen would be fine.