You can do that pretty easily without an extension. Under View>Zoom
select "Zoom text only" which will stick between sessions. Then use
Ctrl+ (that's ctrl plus the plus key) to make the text bigger and Ctrl-
(that's ctrl plus the minus key) to make the text smaller and Ctrl0
(that's ctrl plus the zero key) to reset the zoom.
I don't know of an extension to add the icons you're looking for, but
there may be one.
Dave Pyles