What problem does this address?

The "Back" button is displayed in the Document Bar when switching contexts like Page > Template, Patterns > Edit Original, Template Part in template > Edit is too easy to miss, since it's grey text over grey background.

It's easy to miss and might lead to users relying on the browser's back button, risking content loss.

What is your proposed solution?

This needs more design expertise than I can provide, but since it's already an element, the obvious option would be to make it look more like a button by adding a background, a border, or a different font color than the other elements in the Document Bar.