Hi George, sorry for the slow response. Hope you are doing well!
- You can undo any action in site builder with Ctrl-Z / Cmd-Z or using the undo option in the top left menu.
- You can zoom using your mouse (hold ctrl/cmd and scroll), touchscreen or trackpad (pinch to zoom). I think that is the quickest way to get to a specific zoom level. Please let me know if none of those are working for you.