Add minimize and maximize buttons in Debian 8

I was looking for the same and shortly after reading this question I found the solution for my setup (Debian 8, Gnome-Flashback): The relevant key is in org.gnome.desktop.wm.preferences, "button-layout". Edited with dconf-editor from "appmenu:close" to "appmenu:minimize,maximize,close" and the buttons are back :-)

Regards, Joachim