Specifies the group of buttons on the left and right side of the titlebar.
Specifies the first spacer available (by default the one next to the border of the titlebar).
Specifies the second spacer available (by default the one next to the window title).
The TitlebarLayout is a comma separated list of elements to be placed in the left or right part of the titlebar of windows. Since TitlebarLayout is a MyFrame option, different layouts for different windows are possible.