Your question helped me find an answer to my exact same problem :-)
You were near the solution !
In dconf-editor
, select /org/gnome/gnome-panel/layout
. You will then see 2 names : object-id-list
and toplevel-id-list
.
You have to clean these 2 values in order to go back to a usable interface.
For example, if you have ['menu-bar
', 'menu-bar-1
', 'menu-bar-2
'], you just have to remove menu-bar-1
and menu-bar-2
and leave it at ['menu-bar'].
No need to save or restart anything, it's instantaneous :-)