Metacity is the Gtk+3-based window manager used in Projects/GnomeFlashback.
With metacity, the button layout on window decorations can be configured to change the selection, position and order of buttons in the top corners of a window. This includes the classic window buttons to minimize, maximize and close a window as well as a button that shows the context menu of the window. The button layout on window decorations are managed via the org.gnome.desktop.wm.preferences schema using the button-layout gsettings key.
The following example shows two different button layouts, with one with the menu button on the left and the classic window buttons on the right, and another layout, where the classic window buttons are on the left and no menu button is present:
The currently configured value can be queried via:
gsettings get org.gnome.desktop.wm.preferences button-layout
Valid layout values are minimize, maximize, close, which show buttons with respective functionality on the window border and menu, which shows a hamburger menu that activates the context menu which provides access to additional options such as the "Always on top" option. A colon : is used to specify values for the left and right window corner. Multiple values are separated by comma. To specify the hamburger menu on the left corner and the minimize, maximize and close buttons on the right corner use the following value: menu:minimize,maximize,close.
To set the layout to a particular value use the following command:
gsettings set org.gnome.desktop.wm.preferences button-layout 'menu:minimize,maximize,close'