Funny thing - I also just set up a 2nd account today to test something. The account was local/std and is still on my machine. I'll try removing it and get back to you with what I experience.
Maybe you can check something for me on your machine(s)
Launch File Explorer
change the navigation pane to 'show all folders' (right click, context menu)
expand your user profile in the navigation pane
and select your User profile so that it shows the folder contents in the main pane.
What I and others are seeing is a 'duplication' of the User system folders (Documents, Downloads, Music, Pictures, Videos).
You do not see the 'duplicates' when you go directly to your C:\Users\<username> folder, only when you view it with the User folder delegated to ThisPC.
Shawn helped one member through it, but those things did not help on my machine.
Solved Duplicate subfolders in User folder - Windows 10 Forums
Double Users Folders after 10061 - Windows 10 Forums
Anyway, the 2nd user had the same issue, so I can delete it to see what happens.
Those are two different things.
1) The question raised was about Start menu customization - that is long gone
Seeing the next wave of Start menu changes tells me that the option will NOT return, at least not the way it was: left pane include User folders, Games, and system tools.
2) the area you pointed to concerns the notification area (system tray icons ...)
but ... but... that helps Gary ... Thanks Dick
Look in the drop down system tray
drag the defender Icon to the taskbar area
I don't know if it will 'stick' through a reboot - I'll leave that as an exercise for the student - please let me know if this worked for you - thanks.
F14 provided extra information:
after sticking Defender on the task bar notification area, paste this into the explorer address bar:
Control Panel\All Control Panel Items\Notification Area Icons
!!!!! this won't take you directly there, but the suggestion below the address bar will,
!!!!! don't hit enter - select Control Panel\All Control Panel Items\Notification Area Icons below the address bar
You should see Defender in the list - set it how you want it and see if it sticks.
An aside re: Avast. Some members have reported issues on their machines when Avast was installed on it. This might be the way they have Avast configured or it might be that Avast and Win10 aren't ready for each other. Something to keep in mind if you run into more serious issues (i.e uninstall Avast as a test)