Where this same combination is used for reviews, the button is square around the icon. Something is stretching it out a bit here, and I think we should dig into the styles to figure out why and fix it.
Can we add a little bit of spacing between the button and the filename? The review entry CSS adds margin-right: 0.5rem on the .collapse-btn element.
margin-right: 0.5remon the.collapse-btnelement.