What is this new menubar thing, and how do I configure it?
That is actually a buttonbar, not a menubar. It makes use of the new "button_bar" and "button" imageclasses to draw itself, and is completely user-configurable. The buttonbar can have as many buttons on it as can fit in the horizontal dimensions, and you can have as many buttonbars as you care to define. Each button can be bound to any of the same actions a menuitem or action binding can: a string to be parsed by Eterm, something to echo to the child process, a menu to display, or a script to execute.
In other words, if all you want is a menubar, you can do that. But you can also do much, much more. :-)
In addition, each button can have an icon, text, or both. The ? and X icon buttons in the default theme demonstrate this capability. They also demonstrate "rbuttons," buttons which are right- instead of left-justified. The following config file excerpt shows how a buttonbar is defined:
* button Eterm action menu "Eterm Operations"
* button Font action menu Font
* button Background action menu Background
* button Terminal action menu Terminal
* rbutton icon help.png action script "exec(Eterm -e man Eterm)"
* rbutton icon exit.png action script "exit()"