Why has my camera button/icon disappeared? You know that camera icon that shows up in the right-hand side of the main viewer? Well, it disappeared. I know I can toggle with CTRL-0 but I would really like to know why this happened and what I can do to get it back.
I have looked throughout as many options as I can locate, but no dice.
Here is my viewer:

As you will note, there is no camera button on the right side.
Also: Yes. I have restarted. Would not have posted here without taking a number of steps. No effect. It's like I've toggled something.
Gizmos visibility
You have somehow disabled the gizmos visibility, you can simply re-enable it by pressing the button in the bar: