The equation editor button is only shown when you click the three dots. I was told that this depends on the width of my browser or screen. This is not true in my case. My laptop is at full 1080p/16:9 and my browser is in full screen. At 100% zoom there is still enough space on the toolbars panel to show the equation editor button. To display the button I have to zoom out to a point where the font in my browser is already too small. I recommend that this button be shown by default.