We used this extension to extensively test the behavior, both on ourselves (by daily driving it) and as part of a series of informal user interviews.

One interesting learning from those interviews was that for a lot of people "abstract symbol I don't know" intuitively translates to "menu".

Even though the indicator doesn't have a direct reference to "apps", people tended to click the pill in the top left without thinking when asked to launch apps, since it looked like a menu to them.