Image menu collapsed to "hamburger menu" although not necessary --?

I’m editing a bitmap, and wanted to use the external editor function, but I couldn’t find the IMAGE menu in the Paint window. Finally figured out it was in the “hamburger menu”, but am wondering WHY? I thought the hamburger menus were for when the app had been sized down and there wasn’t adequate space for the full menu presentation. Here’s a screenie of my current layout, there should be plenty of space:

Anyway, it’s annoying, is there a way to refresh the window so that the usual menu appears?

Right click on “hamburger” → Header → Show Menus:

image

Wow, that was obscure. Thanks.