Created attachment 123016 [details] screenshot of button SUMMARY The button in the top corner of desktop used to contain more options than the menu you get by right clicking on the desktop. In particular the "add new panel" entry has recently been removed, so all people used to add panels using that button will no longer find that option. Since that button has been created to provide options to add things to the desktop, if we remove entries from its menu, it no longer makes sense to exist and should be removed at all. plasma-desktop-5.16.90
This bug has been fixed with a rewrite in Plasma 5.18 that has removed the Desktop Toolbox in its current form.