How to expand a hamburger menu

In my Image Editor there is a "hamburger menu" (the icon with three horizontal lines in a stack) that I customized in Blender 2.79 or earlier on a computer with a smaller display. Now I've decided I want to get rid of the hamburger and keep those menu items expanded instead (so that I can see the asterisk that appears by Image* when an image file has been modified since last saved).

Maybe this type of collapsed hamburger menu is not used anymore in recent versions of Blender. I'm not sure. I don't see an option in the menu to expand it again.

How do I revert this part of the menu to the default view? I don't want to load factory settings just to revert this one part of the interface.