Left and right margin for the Preview / Link / Close / “More options” icons are identical (icons are center-aligned).
Left and right margin aren’t center-aligned and the UI looks off (see attached screenshot).
if you’re using sliding panes plugin, you can adjust it in settings -> sliding panes -> spine width. I set it to 40 to make icons centered.
Oh, I forgot I was using that plugin, thanks Joky, that solved it.