Sorry for the problem with the section menu not showing in the recent update. The problem may be related to recent changes where they have moved the menu for certain things into a different area. Here’s a screenshot of the section background editor.
https://www.screencast.com/t/DFVpssaqpSY
Additionally, the Edit Section menu can be seen at the bottom of the block like this:
https://www.screencast.com/t/NgZaTMJfUM0