Opening the Appearance Editor for a character activates the Sculpt Morph overlay (see attached image), which makes it impossible to see any changes that are being made. This happens regardless of whether Sculpt Morph overlay is on or off before the Appearance Editor is launched.

How much of the overlay is shown depends on the setting of Activate Sculpt Morph before the Appearance Editor is launched. So, as a workaround, I set the opacity to the lowest value and select only the Ears overlay, which leaves the face uncovered.

Desired behavior: The Sculpt Morph overlay should be disabled when the Appearance Editor is launched.