Created attachment 92692 [details] Screenshot showing the new menu button DataTables has a built-in option for showing all columns in a table with column configuration. I propose to make that a global feature of the columns configuration menus.
+1 :)
Unfortunately DataTables' built-in option doesn't work with a column which is configured to be both 'Hidden by default' AND 'Cannot be toggled.' I don't know how common that combination is but it wouldn't be good for columns to be appearing unexpectedly. I'll have to see what I can do to accommodate that situation.