The atomic unit. A single row inside the menu that the user can select. Each Menu Item has a left side, a center label, and a right side. The left and right sides hold swappable instances, so you can turn them on or off with a boolean and swap between icon, flag, or avatar on the left, and badge, switch, icon trailing, or shortcut on the right. The center holds a static text label. Because these are instance swaps and not slots, the set of options is fixed to what the master defines.
