The ability to comment on cells in Google Sheets is super useful. The ability to find those comments, however . . . pretty stinkin’ difficult. That little yellow triangle in the corner just ain’t cutting it. In a big spreadsheet, it can be easy to miss some comments.
You can show all of the comments in the currently open spreadsheet tab by either hovering over or clicking on the comments icon on the sheet tab at the bottom. Clicking keeps them open while you move your mouse around or scroll. If you hover, the comments are hidden again as soon as you move your mouse.