I’m not sure, why your buttons are so wide, mine look like this:
The axe is for deleting undercolored segments and low weight segments. I wrote about it in those 2 posts: EyeWire Stats - another TamperMonkey script
You can hover over it to see a tooltip with the info or, at least, should be able to.
And yes, it’s from the Utilities script.
Oh, and there’s a setting in Settings -> Utilities to turn it on/off. It’s called “Show “Remove Undercolor/Low Confidence” button”.