Basic functionality, which for just some odd reason doesn't seem to show on the search bar. I noticed that it is missing when the site is in read-mode and tried to zoom-in, and return the default view scale.
Reader view intercepts the normal zoom keys (for example on Windows: Ctrl+ to enlarge) and applies it as an increase in font size. If you click the Aa on the little vertical toolbar and "zoom" with that Type Controls panel open, you'll see what I mean. Maybe the panel should put the number next to the Aa for quick reference so it's not necessary to open the panel.