Never mind, found it. It is the hidden text button in the Appearance controls in the panel on the right.
Next question (or two):
Why does the hidden text then (when enabled on the right) appear only when selected?
Notice that the slider controls in the Appearance controls are partly obscured. It seems the width of that panel is not adjustable (I tried dragging the left edge). If there is a label for what they do, it is off screen. But, I discovered by experimenting that those are the intensity controls for the named objects. Suggestion: (a) one label at the top perhaps or a hover help hint, and (b) adjustable width for the appearance panel.
Found the drag to resize, here it is. Picture worth a thousand words (see the right side end of the sliders). But the hint does work, “set the opacity of the …” Thank you