>Update: Found more than one Extension that has a word "Incognito" in the title. For example, "Incognito for Chrome", "New Incognito Windows". But the "Incognito for Chrome", even though has only 13 reviews, all positive, 5 stars. Is this the one you suggest?

At least in firefox it's not an add-on but a built-in feature. Press ctrl+shift+p.