I upgraded to plasma 5.12 and the global menus disappeared, and the entry in settings also disappeared.
Application Style ⇒ Widget Style ⇒ Fine Tuning
I tried deleting the plasma* files from ~/.config
and also the whole ~/.kde
folder thinking it may be some misconfiguration, but none of this helped.
Best Answer
According to announcements you need to add the corresponding Plasma Widget or the menu button from "Window Decorations" settings.
Step by step instructions:
From the Application Dashboard/Launcher/Menu, select "Settings" (in the Launcher: under "Applications") → "System Settings" → "Application Style" → "Window Decorations" → "Titlebar Buttons"; then drag and drop the "Application menu" icon to the titlebar.