What I was going to post (in reply to DJohnston):
Thanks. There was no way I could open Dolphin or anything else. None of the key bindings to move to a different desktop worked. There was no applications menu (because there was no panel).
I used REISUB and when I logged in again there was a context menu and panel. The desktop had gone to desktop mode, so I changed it back to folder view and restored the visible environment. In the light of your advice, I will log in as root and restore last night's backup of my home folder.
That particular setting seems to be a dangerous and defective one.
Thanks again.
In the light of Archie's comments, I will leave everything as is until I hear differently.
Strange things happened when I ran BleachBit (as user), then BleachBit Root after logging in again. First, BleachBit (user) tried to delete a lot of system files so I ran BleachBit Root which deleted many files. What is odd is that I ran BleachBit in both roles before the fiasco with the desktops so there should have been very little to delete, especially for BleachBit Root.
My question now is whether to stay with the existing home folder or to restore my latest backup.
