The button is probably configured to show a label, and to place it on the left of the icon.
There's no asymmetry. The whole toolbar is shorter, since you removed the only thing that was taller than all the other elements.
It looks like you have a second file display toolbar under the main one, which makes things look asymmetrical in the screenshot. Most of it is cropped out, but if you zoom in you can see the dividing line between the two toolbars. The top toolbar has the same amount of space above and below it, and the extra space is a second toolbar underneath, at least as far as I can tell from the cropped screenshot.
Oh I see. There is a faint line I didn't see before. It's not out of alignment. The blue colour on the second row is the same as the first one, making it look blended. Sorry.
Did you know SysInternals ZoomIt! has a live zoom that can be invoked with a hotkey. Can auto start with windows, running in the background, no taskbar icon. You can put the global hotkey on an HID device, such as this here Scrolli Boii