I would argue that the minimize actions for both columns in the Content tab are not primary actions hence should noy not be positioned as such.

To me it would make more sense for these actions to be toned down and have a slightly different placement, for instance in the upper, outer corner of each column. You could perhaps also get away with just using an icon for this item (and not an associated label) if the icon was more suitable to the action. The hamburger used has come to be universally known as something that displays a menu, and not necessarily something that toggles something. A variant of an arrow might be a better option.